/usr/lib/python2.7/dist-packages/cogent/seqsim/sequence_generators.py is in python-cogent 1.9-9.
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1422 | #!/usr/bin/env python
"""sequence_generators.py: various types of random and non-random generators.
Currently provides:
SequenceGenerator: fills in degenerate sequences, either by cycling through
all possibilities or by jumping to a particular sequence. Supports indexing,
iteration, and slicing.
Partition: generates all the ways of dividing n objects among b bins. Useful for
stepping through a space of compositions, or dividing a sequence.
The SequencGenerators are fairly elaborate, and allow complex modeling of RNA.
The present implementation is based on Freqs, and is relatively slow. An
array-based implementation that uses seqsim.usage objects, cogent core
alphabets, etc. is in the works, and should have essentially the same interface.
However, this implementation is fairly well-tested and was used to generate
the data for the Knight et al. 2005 NAR paper on hammerhead/isoleucine
motif folding.
"""
from operator import mul
from types import SliceType
from sys import path
from random import choice, random, shuffle, randrange
from cogent.maths.stats.util import Freqs
from cogent.struct.rna2d import ViennaStructure
from cogent.app.vienna_package import RNAfold
from numpy import logical_and, fromstring, byte
__author__ = "Rob Knight"
__copyright__ = "Copyright 2007-2016, The Cogent Project"
__credits__ = ["Rob Knight", "Daniel McDonald"]
__license__ = "GPL"
__version__ = "1.9"
__maintainer__ = "Rob Knight"
__email__ = "rob@spot.colorado.edu"
__status__ = "Development"
IUPAC_DNA = {'T':'T','C':'C','A':'A','G':'G',
'R':'AG','Y':'TC','W':'TA','S':'CG','M':'CA','K':'TG',
'B':'TCG','D':'TAG','H':'TCA','V':'CAG','N':'TCAG'}
IUPAC_RNA = {'U':'U','C':'C','A':'A','G':'G',
'R':'AG','Y':'UC','W':'UA','S':'CG','M':'CA','K':'UG',
'B':'UCG','D':'UAG','H':'UCA','V':'CAG','N':'UCAG'}
def permutations(n, k):
"""Returns the number of ways of choosing k items from n, in order.
Defined as n!/k!
"""
#Validation: k must be be between 0 and n (inclusive), and n must be >=0.
if k > n:
raise IndexError, "can't choose %s items from %s" % (k, n)
elif k < 0:
raise IndexError, "can't choose negative number of items"
elif n < 0:
raise IndexError, "can't choose from negative number of items"
product = 1
for i in xrange(n-k+1, n+1):
product *= i
return product
def combinations(n, k):
"""Returns the number of ways of choosing k items from n.
Defined as n!/(k!(n-k)!)
"""
#Validation: k must be be between 0 and n (inclusive), and n must be >=0.
if k > n:
raise IndexError, "can't choose %s items from %s" % (k, n)
elif k < 0:
raise IndexError, "can't choose negative number of items"
elif n < 0:
raise IndexError, "can't choose from negative number of items"
#permutations(n, k) = permutations(n, n-k), so reduce computation by
#figuring out which requires calculation of fewer terms.
if k > (n - k):
larger = k
smaller = n - k
else:
larger = n - k
smaller = k
product = 1
#compute n!/(n-larger)! by multiplying terms from n to (n-larger+1)
for i in xrange(larger+1, n+1):
product *= i
#divide by (smaller)! by multiplying terms from 2 to smaller
for i in xrange(2, smaller+1): #no need to divide by 1...
product /= i #ok to use integer division: should always be factor
return product
def _slice_support(the_slice, length):
"""Takes a slice and the length of an object; returns normalized version.
Specifically, corrects start and end for negative indices.
"""
start = the_slice.start
stop = the_slice.stop
step = the_slice.step or 1
#fill in missing values for start and end
if start is None:
start = 0
if stop is None:
stop = length
#convert end-relative values to start-relative values
if start < 0:
start = length - start
if stop < 0:
stop = length - stop
return (start, stop, step)
#ensure step is not zero, or we never move in the sequence!
if not step:
step = 1
class SequenceGenerator(object):
"""Generates all the possibilities for a degnerate template."""
def __init__(self, template='', alphabet=None, start=None):
"""Returns a new SequenceGenerator based on template"""
if alphabet:
self.Alphabet = alphabet
else:
self.Alphabet = IUPAC_RNA
self.Template = template
if start:
self.validate(start)
self.Start = start
else:
self.Start = [0] * len(template)
def validate(self, state):
"""Check that state is allowable given the template."""
possibilities = map(len, map(self.Alphabet.__getitem__, self.Template))
for max_allowed, curr in zip(possibilities, state):
if curr >= max_allowed:
raise ValueError, "Tried to set a state to too high an index."
def __str__(self):
"""Returns data about current iterator's template"""
return "<SequenceGenerator object with template: %s, and alphabet: %s>"\
% (self.Template, self.Alphabet)
def __len__(self):
"""Returns the number of elements in all possible expansions."""
return self.numPossibilities()
def numPossibilities(self):
"""Same as __len__, except Python doesn't coerce result to an int"""
if self.Template:
return reduce(mul, map(len, map(self.Alphabet.__getitem__, \
self.Template)))
else:
return 0
def _index2state(self, index):
"""Takes an index and returns the corresponding state."""
expansions = map(self.Alphabet.__getitem__, self.Template)
num_items = len(expansions)
lengths = map(len, expansions)
indices = range(num_items)
indices.reverse() #want to traverse in reverse order
states = [0] * num_items #initialize with zero
for i in indices:
if not index:
break #if index is zero, so is everything to the left of i
if lengths[i] == 1:
continue #skip anything that can't vary
else:
choices = lengths[i]
states[i] = index % choices
index //= choices
return states
def __getitem__(self, index):
"""Supports indexing. Now uses constant-time algorithm (fast)."""
if type(index) is SliceType:
return self._handle_slice(index)
else:
if index < 0:
index = self.__len__() + index
iterator = self.items(self._index2state(index))
return iterator.next()
def _handle_slice(self, index):
"""Needs separate method, since __getitem__ can't yield _and_ return.
"""
length = self.__len__() #might be too big to fit in an int
start, stop, step = _slice_support(index, length)
#quick check to se if we can't return any items
if (stop - start < 1):
raise StopIteration
if step < 1:
raise NotImplementedError, \
"Can't support negative step in irreversible sequence."""
else:
index = start
iterator = self.items(self._index2state(start))
while index < stop:
for i in range(step - 1):
if i >= stop - 1:
raise StopIteration
iterator.next()
index += step
yield iterator.next()
def __iter__(self):
"""Iterator interface using self.Start as the start_state."""
return self.items(self.Start)
def items(self, start_state=None):
"""Acts like a sequence containing all the possibilities."""
#shortcut if the template is empty
if not self.Template:
return
#figure out how many possibilities there are at each position, and
#what the choices are
expansions = map(self.Alphabet.__getitem__, self.Template)
num_positions = len(expansions)
lengths = map(len, expansions)
#set the starting state, i.e. the array of what the current choice is
#at each position.
if start_state is None:
indices = [0] * num_positions
else:
self.validate(start_state)
indices = start_state[:]
seq = [expansions[i][indices[i]] for i in range(num_positions)]
#always return the sequence for the first possibility: there might not
#be any more...
yield ''.join(seq)
while 1:
#find rightmost element that can be incremented
pos = num_positions - 1
while indices[pos] == lengths[pos] - 1:
pos -= 1
if pos < 0: #ran off end
return
indices[pos] += 1
seq[pos] = expansions[pos][indices[pos]]
#reset the rest of the elements, if there are any
pos += 1
while pos <= num_positions - 1:
indices[pos] = 0
seq[pos] = expansions[pos][0]
pos += 1
#seq should always contain a list of the current states for each pos
yield ''.join(seq)
class Partition(object):
"""Generator behaving like a list of the partitions of a set of n items.
Usage: p = Partition(num_items, num_pieces, min_occupancy=0)
Requires each bin to have at least min_occupancy pieces.
"""
def __init__(self, num_items, num_pieces, min_occupancy=0):
"""Returns new Partition object with first partitions initialized.
Usage: p = Partition(num_items, num_pieces, min_occupancy=0)
Default is min_occupanct items in each bin, with all the leftovers
in the first bin.
"""
self.NumItems = num_items
if num_pieces:
self.NumPieces = num_pieces
else:
raise ValueError, "Cannot divide items among zero bins."
self.MinOccupancy = min_occupancy
self._reset()
def __str__(self):
"""Prints string representation with pieces, items, and occupancy."""
return "Items: %s Pieces: %s Min Per Piece: %s" % \
(self.NumItems, self.NumPieces, self.MinOccupancy)
def _validate(self, states):
"""Verify that states has right sum and meets occupancy restrictions.
Raises ValueError if there is any problem: does not return anything.
"""
num_pieces = self.NumPieces
min_occupancy = self.MinOccupancy #cache for efficiency
#check the number of pieces
if len(states) != num_pieces:
raise ValueError, "Tried to set state %s, but need %s pieces." % \
(states, num_pieces)
#check that no piece has too few items
sum = 0
for state in states:
if state < min_occupancy:
raise ValueError, \
"Tried to set state %s, but need at least %s items per bin." %\
(states, min_occupancy)
sum += state
#check that we have the right number of pieces
if sum != self.NumItems:
raise ValueError, \
"Tried to set state %s, but it has %s pieces instead of %s." %\
(states, sum, self.NumItems)
def _reset(self, states=None):
"""Resets to a particular state given by sequence of states in each bin.
Default: go to first partition, with MinOccupancy items in each bin and
any leftovers in the first bin.
"""
min_occupancy = self.MinOccupancy
num_items = self.NumItems
num_pieces = self.NumPieces #cache for efficiency
if states:
#check that we're not trying to set a bad state
self._validate(states)
self._bins = states
else:
reserved = (num_pieces - 1) * min_occupancy
#check that we can actually divide the pieces among the bins OK
if reserved + min_occupancy > num_items:
raise ValueError, \
"Can't divide %s items into %s pieces with at least %s in each."\
% (num_items, num_pieces, min_occupancy)
#otherwise, fill the bins
bins = [min_occupancy] * num_pieces
bins[0] = num_items - reserved
self._bins = bins
self._reserved = reserved
def __iter__(self):
"""Defines iterator interface, starting with self._bins."""
return self.items()
def _transform(self, value):
"""Transformation to be applied to return values.
Default behavior is to copy, but can be overridden in derived classes.
"""
return value[:]
def items(self, bin_states=None):
"""Defines iterator interface, supporting for i in self."""
#always copy the array of states, since we will be mutating it
if bin_states:
self._validate(bin_states)
bins = bin_states[:]
else:
self._reset()
bins = self._bins[:]
#cache local vars for efficiency
delta = self.MinOccupancy
num_items = self.NumItems
num_pieces = self.NumPieces
transform = self._transform
end_state = num_items - (delta * (num_pieces - 1))
#always return the first state
yield transform(bins)
while 1:
#check if we're done: when the last bin has all the items
if bins[-1] == end_state:
return
#need to adjust the bins to the correct state for next time
#find rightmost non-delta except the last
rightmost = sum = 0
#figure out the sum of all the items to the right of the bin we're
#going to decrement, and also which bin we're going to decrement
for i in xrange(len(bins)-2, -1, -1):
curr = bins[i]
if curr != delta:
rightmost = i
break
else:
sum += curr
#bins[-1] excluded from count above: also need to add 1 for newly
#incremented item from the rightmost decrementable bin
sum += bins[-1] + 1
bins[rightmost] -= 1
#leftover_bins counts the number of bins more than one to the left
#of the rightmost
leftover_bins = num_pieces - rightmost - 2
if leftover_bins:
bins[rightmost+2:] = [delta] * leftover_bins
sum -= delta * leftover_bins
bins[rightmost + 1] = sum
yield transform(bins)
def __len__(self):
"""Calculates the number of possible parameters with current state.
Specifically, only takes into account the number of objects, the
number of bins, and the minimum per bin: does _not_ take into account
a particular start point.
"""
#NOTE: I don't know why the following works, but it seems to be
#empirically true when compared to the lengths of the resulting lists.
cuts = self.NumPieces
items = self.NumItems - (self.MinOccupancy - 1) * cuts
product = 1
for i in range(items - cuts + 1, items):
product *= i
for i in range(2, cuts):
product /= i
return product
class Composition(Partition):
"""Generates evenly spaced composition intervals over an alphabet.
Usage:c=Composition(spacing,min_occupancy=0,alphabet='ACGU')
spacing should be a float representing the percentage of the space
separating successive values (e.g. 5 for 5% steps). Note that the spacing
may be approximated: check self.Spacing to see what the recorded value is.
alphabet should be a list, in order, of the possible characters.
min_occupancy should typically be 0 (can miss some symbols) or 1 (always
require at least one of each symbol).
Always yields an un-normalized Freqs containing counts of
each symbol at each step.
For a given alphabet A, the possible compositions of that alphabet can
be represented as a simplex in len(A)-1 dimensions. Composition returns
a representation of evenly distributed compositions in that space, with
distances along all dimensions represented by spacing (i.e. if spacing
is 0.05, then the next point in any dimension will be 0.05 away if it
exists.)
Useful for generating sequences of specified composition that can then
be randomized.
"""
def __init__(self,spacing,min_occupancy=0,alphabet='ACGU'):
"""Initializes new generator with specified spacing, alphabet, etc.
Usage: c = Composition(spacing, min_occupancy=0,
alphabet='ACGU')
See class documentation for details.
"""
self.Spacing = spacing #also sets self._num_items
self.Alphabet = alphabet #also sets self._num_pieces
self.MinOccupancy = min_occupancy
def _get_spacing(self):
"""Accessor for self.Spacing."""
return self._spacing
def _set_spacing(self, spacing):
"""Mutator for self.Spacing. Sets self.NumItems to correct value."""
num_items = int(round(100.0/spacing))
self._num_items = num_items
self._spacing = 100.0/num_items
Spacing = property(_get_spacing, _set_spacing, \
doc="Set spacing and calculate string length.")
def _get_num_items(self):
"""Accessor for self.NumItems."""
return self._num_items
def _set_num_items(self, num_items):
"""Mutator for self.NumItems: recalculates self.Spacing."""
self._num_items = num_items
self._spacing = 100.0/num_items
NumItems = property(_get_num_items, _set_num_items, \
doc="Set NumItems and calculate Spacing.")
def _get_alphabet(self):
"""Accessor for self.Alphabet."""
return self._alphabet
def _set_alphabet(self, alphabet):
"""Mutator for self.Alphabet."""
self._alphabet = alphabet
Alphabet = property(_get_alphabet, _set_alphabet, \
doc="Set alphabet and calculate number of pieces.")
def _get_num_pieces(self):
"""Accessor for self.NumPieces"""
return len(self.Alphabet)
NumPieces = property(_get_num_pieces, doc="Get number of pieces.")
def _transform(self, value):
"""Override superclass transform to yield Freqs.
"""
return Freqs(dict(zip(self.Alphabet, value)))
def __iter__(self):
"""Defines iterator interface, starting with self._bins."""
return self.items()
class MageFrequencies(object):
"""Takes a Freqs and optionally a label.
Writes out a Mage-format string.
This presentation class is standalone to avoid cluttering
Freqs.
"""
def __init__(self, freqs, label=''):
"""Returns a new MageFrequencies object.
This is basically a labeled Freqs that can write itself
out as a Mage-format string.
"""
self.Freqs = freqs#don't mutate original
self.Label = label
def __str__(self):
"""Returns the frequency string, suitable for MAGE."""
pieces = []
freqs = self.Freqs
known_bases = Freqs({
'A':freqs.get('A',0),
'C':freqs.get('C',0),
'U':freqs.get('U',0) + freqs.get('T',0),
'G':freqs.get('G',0),
})
#frequencies should sum to 1 for MAGE display.
known_bases.normalize()
#Only append label field if there is one.
label = self.Label or ''
if label:
pieces.append('{%s}' % self.Label)
for item in 'ACG':
pieces.append(str(known_bases[item]))
return ' '.join(pieces)
class SequenceHandle(list):
"""Holds mutable sequence that can join itself together as string.
Sequence cannot vary in length.
"""
def __init__(self, data='', alphabet=None):
"""Initializes new list over an alphabet. Rejects invalid entries."""
if alphabet:
for d in data:
if d not in alphabet:
raise ValueError, "Item %s not in alphabet %s." \
% (d, alphabet)
super(SequenceHandle, self).__init__(data)
self.Alphabet = alphabet
def __setitem__(self, index, item):
"""Checks that the item is in the alphabet."""
alphabet = self.Alphabet
if alphabet:
try:
absent = item not in alphabet
except TypeError:
raise ValueError, "Item %s not in alphabet %s." \
% (item, alphabet)
else:
if absent:
raise ValueError, "Item %s not in alphabet %s." \
% (item, alphabet)
super(SequenceHandle, self).__setitem__(index, item)
def __setslice__(self, start, stop, values):
"""Checks that items are in alphabet, and that slice is same length."""
orig_length = len(self)
alphabet = self.Alphabet
if alphabet:
for v in values:
try:
absent = v not in alphabet
except TypeError:
raise ValueError, "Item %s not in alphabet %s." \
% (v, alphabet)
else:
if absent:
raise ValueError, "Item %s not in alphabet %s." \
% (v, alphabet)
super(SequenceHandle, self).__setslice__(start, stop, values)
if len(self) != orig_length:
raise ValueError, "Cannot change length of SequenceHandle."
def __str__(self):
"""Returns self as a string, symbols joined."""
try:
return ''.join(self)
except: #use built-in conversion methods for lists
return super(SequenceHandle, self).__str__()
def _naughty_method(self, *args, **kwargs):
"""Prevent other methods that change the length or set items."""
raise NotImplementedError, \
"May not change length of SequenceHandle."
#note how _many_ methods are naughty...
__delitem__ = __delslice__ = __iadd__ = __imul__ = append \
= extend = insert = pop = remove = _naughty_method
class BaseFrequency(Freqs):
RNA = ['U', 'C', 'A', 'G']
DNA = ['T', 'C', 'A', 'G']
"""Holds information about base frequencies."""
def __init__(self, freqs, RNA=True):
"""Returns new BaseFrequency object, ensuring a count for each base."""
if RNA:
alphabet = self.RNA
else:
alphabet = self.DNA
super(BaseFrequency, self).__init__(freqs, alphabet)
for k in alphabet:
if k not in self:
self[k] = 0.0
class PairFrequency(Freqs):
"""Makes a frequency distribution of pairs from freqs of single items."""
def __init__(self, freqs, pairs=None):
"""Makes pair frequency distribution.
Usage: p = PairFrequency(freqs, pairs)
freqs is the single-item frequencies
pairs is the list of valid pairs from which samples will be drawn.
If pairs is None (the default), constructs all possible pairs.
"""
symbol_freqs = BaseFrequency(freqs)
if pairs is None:
symbols = symbol_freqs.keys()
pairs = [(i, j) for i in symbols for j in symbols]
pair_freqs = {}
for i, j in pairs:
try:
pair_freqs[(i,j)] = symbol_freqs[i]*symbol_freqs[j]
except KeyError, e:
print symbol_freqs
print i, j
raise e
super(PairFrequency, self).__init__(pair_freqs, pairs)
self.normalize()
class BasePairFrequency(PairFrequency):
"""Holds information about base pair frequencies."""
WatsonCrick = [('A','U'), ('U','A'),('G','C'),('C','G')]
Wobble = WatsonCrick + [('G','U'), ('U','G')]
def __init__(self, freqs, GU=True):
if GU:
pairs = self.Wobble
else:
pairs = self.WatsonCrick
super(BasePairFrequency, self).__init__(freqs, pairs)
class RegionModel(object):
"""Holds probability model for constructing random or randomized sequences.
Supports the following interface:
Current: Reference to current sequence, or tuple of references.
Template: Degenerate sequence specifying the class of sequences to
produce. Immutable.
Length: Length of the current sequence. Read-only.
Composition: Composition used to generate sequences (e.g. pairs).
refresh(): Generate the next, random sequence.
monomers(f): Update internal frequencies using symbol frequencies in f.
Base class RegionModel behavior is to model a constant region.
"""
def __init__(self, template='', composition=None):
"""Return a new RegionModel object. See class for documentation."""
self.Composition = composition
self.Template = template #will set self.Current
def _get_template(self):
"""Accessor method for self.Template"""
return self._template
def _set_template(self, data):
"""Mutator method for self.Template"""
self._template = data
self.Current = SequenceHandle(data)
self.refresh()
Template = property(_get_template, _set_template)
def _get_composition(self):
"""Accessor method for self.Composition"""
return self._composition
def _set_composition(self, composition):
"""Mutator method for self.Composition"""
self._composition = composition
self.refresh()
Composition = property(_get_composition, _set_composition)
def __len__(self):
"""Returns length of the current string."""
return len(self.Current)
def refresh(self):
"""Replaces the current sequence with a new string fitting the model.
Does nothing unless overridden in derived classes.
"""
pass
def monomers(self, composition, **kwargs):
"""Replaces the current composition with new Freqs."""
self.Composition = composition #no effect unless overridden
class ConstantRegion(RegionModel):
"""Holds a constant string: this is default behavior."""
pass
class UnpairedRegion(RegionModel):
"""Holds an unpaired region: this gets filled in from self.Composition."""
def refresh(self):
"""Fills in a sequence drawn randomly from composition."""
if hasattr(self, "Current") and self.Current and self.Composition:
self.Current[:] = self.Composition.randomSequence(len(self))
class ShuffledRegion(RegionModel):
"""Holds a non-degenerate template that is randomized by shuffling."""
def refresh(self):
"""Randomizes the template by permuting the elements."""
if hasattr(self, "Current") and self.Current:
shuffle(self.Current)
class PairedRegion(RegionModel):
"""Holds complementary upstream and downstream strands."""
def refresh(self):
"""Fills in tuple of paired sequences drawn from self.Composition."""
if hasattr(self, "Current") and self.Current and self.Composition:
length = len(self)
upstream = self.Current[0]
downstream = self.Current[1]
pairs = self.Composition.randomSequence(length)
for i in xrange(length):
upstream[i] = pairs[i][0]
downstream[i] = pairs[i][1]
#downstream has the complements, but need to reverse it as well
downstream.reverse()
def __len__(self):
"""Returns length of (half of) the current helix, not the tuple..."""
return len(self.Current[0])
def _set_template(self, data):
"""Mutator method for self.Template"""
data = list(data)
self._template = data
self.Current = (SequenceHandle(data), SequenceHandle(data))
self.refresh()
#Override base class _set_template in the property
Template = property(RegionModel._get_template, _set_template)
def monomers(self, composition, **kwargs):
"""Calculates pair distribution from monomer frequencies."""
GU = kwargs.get('GU', True)
self.Composition = BasePairFrequency(composition,GU)
class DegenRegion(RegionModel):
"""Handles a string of degenexerate bases.
WARNING: Not tested!
"""
def refresh(self):
"""Fills in degen bases randomly according to possible symbols"""
if hasattr(self, "Current") and self.Current and self.Composition:
result = []
non_degen = dict.fromkeys('UCAG')
freqs = self.Composition
for b in self.Template:
if b in non_degen:
result.append(b)
else:
allowed_bases = IUPAC_RNA[b]
composition = Freqs(dict([(i,freqs[i]) for i in allowed_bases]))
composition.normalize()
result.append(composition.choice(random()))
self.Current[:] = ''.join(result)
###WARNING: MATCHINGREGION HAS NOT YET BEEN TESTED####
class MatchingRegion(RegionModel):
"""Fills in the complement to specified constant region."""
WatsonCrick = {'A':'U', 'U':'A', 'C':'G', 'G':'C'}
Wobble = {'A':'U', 'U':'AG', 'C':'G', 'G':'UC'}
def __init__(self):
raise NotImplementedError, "NOT YET TESTED"
def _init_current(self):
"""Initializes Current and some private variables."""
wc = self.WatsonCrick
template = self.Template
self.Complement = [wc[base] for base in template]
self.Current = SequenceHandle(self.Complement)
self._freqs = {}
def refresh(self):
"""Returns new sequence that could pair with template."""
if self.GU:
freqs = self._freqs
bases = [freqs[base].randomSequence(1)[0] for base in self.Template]
self.Current[:] = bases
else:
self.Current[:] = self.Complement
def monomers(self, freqs, **kwargs):
"""Calculates Freqs of possibilities for each base."""
if kwargs.get('GU', False):
pairs = self.Wobble.items()
self.GU = True
for base, complements in pairs:
freqs = self.Composition.copy()
freqs.subset(complements)
freqs.normalize()
self._freqs[base] = freqs
else:
self.GU = False
class SequenceModel(object):
"""Stores state associated with generating a randomized sequence."""
def __init__(self, order, composition=None, GU=True, \
constants=[], unpaireds=[], helices=[], matches=[], degenerates=[]):
"""Returns a new SequenceModel.
constants, unpaireds, and helices should all be lists of RegionModels.
order should be a string of the following format:
[label1][index1] [label2][index2] ...
where label is C for constant, U for unpaired, or H for helix,
or D for degen,
and index is the index of the region within the appropriate list.
Use hyphens to indicate cuts.
For example:
"C0 U3 H1 U5 - H2 C1 H2 H1 U0"
...means constants[0] followed by unpaireds[3], followed by the
first part of helices[1], followed by unpaireds[5], followed
by the first part of helices[2], followed by constants[1],
followed by the second part of helices[2], followed by the
second part of helices[1], followed by unpaireds[0].
There is a cut in the sequence between U5 and H2.
Although this is a very general mechanism (each piece can potentially
have its own composition, etc.), typically the functionality will be
accessed programatically through other classes.
"""
self.Helices = helices
self.Unpaireds = unpaireds
self.Constants = constants
self.Degenerates = degenerates
self.Matches = matches
self.GU = GU
#Don't _require_ a composition to be passed in, but if it isn't passed
#in, then all the pieces must be initialized with their own compositions
#beforehand.
self.Composition = composition
self.Order = order
def __len__(self):
"""Figures out the total length of all the components."""
length = 0
for i in self.Unpaireds + self.Constants + self.Matches + self.Degenerates:
length += len(i)
for h in self.Helices:
length += 2 * len(h)
return length
def refresh(self):
"""Delegates each region to refresh itself."""
for i in self.Helices + self.Unpaireds + self.Matches + self.Degenerates:
i.refresh()
def _get_order(self):
"""Accessor for self.Order."""
return self._order
def _set_order(self, order):
"""Figure out the order to put pieces in, using string format."""
result = []
segments = order.split('-')
helix_counts = [0] * len(self.Helices)
for s in segments:
pieces = []
components = s.split()
for c in components:
label = c[0]
index = int(c[1:])
if label == 'C': #constant
pieces.append(self.Constants[index].Current)
elif label == 'U': #unpaired random region
pieces.append(self.Unpaireds[index].Current)
elif label == 'D': #degenerate region
pieces.append(self.Degenerates[index].Current)
elif label == 'H': #helix
pieces.append(self.Helices[index].Current[\
helix_counts[index]])
helix_counts[index] += 1
#will give IndexError if the helix is added too many times
else:
raise ValueError, \
"SequenceModel got unknown label: %s" % label
result.append(pieces)
self._order = result
self.refresh()
Order = property(_get_order, _set_order, \
doc="Stores order for accessing the pieces of the template.")
def _get_composition(self):
"""Accessor for Composition."""
return self._composition
def _set_composition(self, composition):
"""Sets the composition of each of the components to a global value."""
if composition:
for i in self.Helices + self.Unpaireds + self.Matches + self.Degenerates:
i.monomers(composition, GU=self.GU)
self._composition = composition
Composition = property(_get_composition, _set_composition)
def _get_GU(self):
"""Accessor for GU."""
return self._GU
def _set_GU(self, GU):
"""Mutator for GU. Recalculates composition."""
self._GU = GU
if hasattr(self, 'Composition') and self.Composition:
self.Composition = self.Composition #recalculate with GU
GU = property(_get_GU,_set_GU,doc="Controls whether GU pairs are allowed.")
def __getitem__(self, index):
"""Returns the index'th segment of the sequence in its current state."""
return ''.join([str(i) for i in self.Order[index]])
def __str__(self):
return '-'.join(self)
class Rule(object):
"""Holds information about pairing constraints on motifs."""
def __init__(self, upstream_seq, upstream_pos, downstream_seq, \
downstream_pos, length):
"""Initialize new Rule object."""
self.UpstreamSequence = upstream_seq
self.UpstreamPosition = upstream_pos
self.DownstreamSequence = downstream_seq
self.DownstreamPosition = downstream_pos
self.Length = length
self.validate()
def validate(self):
"""Sanity checks on rule object."""
if self.Length <= 0:
raise ValueError, "Helix length must be at least 1."
if self.Length > self.DownstreamPosition + 1:
raise ValueError, \
"Helix length cannot be more than 1 greater than downstream start."
if min(self.UpstreamSequence, self.UpstreamPosition, \
self.DownstreamSequence, self.DownstreamPosition) < 0:
raise ValueError, \
"All sequences and positions must be >= 0."
if self.UpstreamSequence == self.DownstreamSequence:
if self.UpstreamPosition >= self.DownstreamPosition:
raise ValueError, \
"Upstream position must have lower index than downstream."
if self.DownstreamPosition-self.UpstreamPosition+1 < 2*self.Length:
raise ValueError, "Helices can't overlap."
if self.UpstreamSequence > self.DownstreamSequence:
raise ValueError, "Upstream sequence must have the smaller index."
def isCompatible(self, other):
"""Checks that the helices in self and other don't overlap.
Has to try all possible combinations of upstream and downstream
sequences, since any could conflict.
"""
if self.UpstreamSequence == other.UpstreamSequence:
diff = abs(self.UpstreamPosition - other.UpstreamPosition)
if self.UpstreamPosition <= other.UpstreamPosition:
if diff < self.Length:
return False
elif diff < other.Length:
return False
if self.DownstreamSequence == other.DownstreamSequence:
diff = abs(self.DownstreamPosition - other.DownstreamPosition)
if self.DownstreamPosition >= other.DownstreamPosition:
if diff < self.Length:
return False
elif diff < other.Length:
return False
if self.UpstreamSequence == other.DownstreamSequence:
diff = abs(self.UpstreamPosition - other.DownstreamPosition)
#only need to check if position in self <= position in other
if self.UpstreamPosition <= other.DownstreamPosition:
if diff < (self.Length + other.Length - 1):
return False
if self.DownstreamSequence == other.UpstreamSequence:
diff = abs(self.DownstreamPosition - other.UpstreamPosition)
#only need to check if position in self >= position in other
if self.DownstreamPosition >= other.UpstreamPosition:
if diff < (self.Length + other.Length - 1):
return False
#if none of the checks failed, return True
return True
def fitsInSequence(self, upstream):
"""Checks whether upstream sequence is too short to hold helix.
Note: downstream sequence length doesn't need to be checked because
the index that can't be overlapped is always 0.
"""
if self.UpstreamPosition + self.Length > len(upstream):
return False
else:
return True
def __str__(self):
"""Human-readable rule string."""
return "Up Seq: %s Up Pos: %s Down Seq: %s Down Pos: %s Length: %s" % \
(self.UpstreamSequence, self.UpstreamPosition, \
self.DownstreamSequence, self.DownstreamPosition, self.Length)
class Module(object):
"""Holds information about a module's required sequence and structure."""
def __init__(self, sequence, structure):
"""Returns a new Module object with specified sequence and structure."""
self.Sequence = sequence
self.Structure = structure
len(self) #will raise error if lengths out of sync
def __len__(self):
"""Returns length of sequence and structure."""
seq = self.Sequence
struct = self.Structure
seq_length = len(seq)
if seq_length != len(struct):
raise ValueError, \
"Lengths of sequence '%s' and structure '%s' differ." % \
(seq, struct)
else:
return seq_length
def __str__(self):
"""Returns string containing sequence and structure."""
return "Sequence: %s\nStructure: %s" % (self.Sequence, self.Structure)
def matches(self, other, index=None, alphabet=IUPAC_RNA):
"""Tests whether sequence/structure in self match other at index.
other must be an object that has Sequence and Structure properties.
If index is None, will search for matches anywhere in other.
###THIS METHOD NEEDS ATTENTION: move responsibility for finding matches
to the sequence objects themselves?
"""
length = len(self)
if not length: #zero-length pattern matches everywhere by definition
return True
if index is not None: #index might be 0...
seq_match = True
this_seq = self.Sequence
other_seq = other.Sequence
for i in range(length):
curr = False
try:
curr = curr or (other_seq[i+index] in alphabet[this_seq[i]])
except:
pass
if not curr:
try:
curr = curr or (this_seq[i] in \
alphabet[other_seq[i+index]])
except:
pass
if not curr:
seq_match = False
break
struct_match = self.structureMatches(other.Structure, index)
return seq_match and struct_match[0]
else:
other_length = len(other)
seq = self.Sequence
struct = self.Structure
other_struct = other.Structure
other_seq = other.Sequence
curr = 0 #current index
while curr <= other_length - length: #don't run off end
try:
index = other_seq.index(seq, curr)
except ValueError:
return False #no more matches to try
if struct == other_struct[index:index+length]:
return True #found struct and seq matches at same place
if curr == index:
curr += 1 #always make sure curr is incremented
else:
curr = index
return False #must have been a seq match but no struct match
#at last window if we got here after the loop
def structureMatches(self, structure, index):
"""Tests whether structure in self matches other at index.
structure must have PairList property, e.g. ViennaStructure.
"""
length = len(self)
if not length: #zero-length pattern matches everywhere by definition
return (True, )
else:
ss = fromstring(self.Structure, byte)
structure_mask = ss != ord('x')
diffs = ss != fromstring(structure[index:index+length], byte)
result = not logical_and(diffs, structure_mask).any()
return result, ss, structure_mask, diffs
class Motif(object):
"""Holds sequences and structures for a motif."""
def __init__(self, modules, rules):
"""Initializes motif with sequences, structures, and rules"""
self.Modules = modules
self.Rules = rules
self.validate()
def validate(self):
"""Checks that sequences and structures are equal length, and rules ok.
Specifically, there must be the same number of sequences as structures;
the length of each sequence must be the length of each structure; and
the rules may not refer to any index outside the known sequences and
structures.
"""
self._check_helix_lengths()
self._check_rule_overlaps()
def _check_helix_lengths(self):
"""Check upstream sequence of each rule to make sure the helix can fit."""
for r in self.Rules:
if not r.fitsInSequence(self.Modules[r.UpstreamSequence].Sequence):
raise ValueError, "Rule '%s' can't fit in sequence '%s'." \
% (r, self.Modules[r.UpstreamSequence].Sequence)
def _check_rule_overlaps(self):
"""Check every pair of rules for overlaps in covered regions."""
rules = self.Rules #cache reference for efficiency
for first in range(len(rules)):
first_rule = rules[first]
for second in range(first):
second_rule = rules[second]
if not first_rule.isCompatible(second_rule):
raise ValueError, "Rules '%s' and '%s' incompatible." \
% (first, second)
def _check_rule_match(self, rule, pairlist, locations):
"""Check whether rule matches pairlist given module locations.
pairlist should be a list where, for each position in a longer sequence,
parlist[i] should be the index of the partner of i, or None if i is
not paired.
locations should be a list of the locations of each module, in the order
that the rule expects to find them.
"""
start_up = locations[rule.UpstreamSequence]+rule.UpstreamPosition
start_down = locations[rule.DownstreamSequence]+rule.DownstreamPosition
for i in range(rule.Length):
if pairlist[start_up + i] != start_down - i:
return False
return True #if nothing failed, everything must be OK
def _get_rule_match_pairs(self, rule, pairlist, locations):
"""Get the pairs that the rule will check."""
start_up = locations[rule.UpstreamSequence]+rule.UpstreamPosition
start_down = locations[rule.DownstreamSequence]+rule.DownstreamPosition
return [(start_up+i,start_down-i) for i in range(rule.Length)]
def matches(self, sequence, structure, positions):
"""Checks that sequence and structure matches motifs/rules.
sequence needs to support the string interface (specifically, s.index)
if it is necessary to search for matches anywhere; otherwise, arbitrary
sequences should work.
structure must have a PairList property (like ViennaStructure),
which is a list the same length as the sequence where the value of
each position is the index of its partner, or None if it is unpaired.
As with sequence, must support string interface to find arbitrary
matches; arbitrary sequences are ok otherwise.
positions must be a list the same length as self.Modules, containing the
index at which each successive module should be searched for.
###TO BE IMPLEMENTED: IF POSITIONS IS NONE, SEARCH FOR THE MODULES
ANYWHERE IN THE SEQUENCE.###
"""
full_length = Module(sequence, structure) #more convenient as object
modules = self.Modules
if len(positions) != len(modules):
raise ValueError, "len(positions) must match number of modules."
for position, module in zip(positions, modules):
if not module.matches(full_length, position):
return False
#can only get here if all the modules matched: need to check rules
pairlist = structure.toPartners()
for rule in self.Rules:
if not self._check_rule_match(rule, pairlist, positions):
return False
#if we got here, all the modules matched and all the rules were OK
return True
def structureMatches(self, structure, positions, offsets=None,debug=False):
"""Checks that structure only matches motifs/rules.
structure must have a PairList property (like ViennaStructure),
which is a list the same length as the sequence where the value of
each position is the index of its partner, or None if it is unpaired.
As with sequence, must support string interface to find arbitrary
matches; arbitrary sequences are ok otherwise.
positions must be a list the same length as self.Modules, containing the
index at which each successive module should be searched for.
###TO BE IMPLEMENTED: IF POSITIONS IS NONE, SEARCH FOR THE MODULES
ANYWHERE IN THE SEQUENCE.###
"""
modules = self.Modules
if len(positions) != len(modules):
raise ValueError, "len(positions) must match number of modules."
if offsets:
positions = [p+o for p, o in zip(positions, offsets)]
result = True
for position, module in zip(positions, modules):
matched, ss, mask, diffs = \
module.structureMatches(structure, position)
if debug:
print 'STRUC:', structure[position:position+len(ss)]
print 'SS :', ss.tostring()
print 'MASK :', ''.join(map(str, map(int, mask)))
print 'DIFFS:', ''.join(map(str, map(int,diffs)))
print 'WHERE:'
all = ['.'] * len(structure)
all[position:position+len(ss)] = ['x']*len(ss)
print ''.join(all)
if not matched:
if debug:
result = False
else:
return False
if not result:
return False
#can only get here if all the modules matched: need to check rules
pairlist = structure.toPartners()
for rule in self.Rules:
if debug:
pairs = self._get_rule_match_pairs(rule, pairlist, positions)
for up, down in pairs:
all = ['.'] * len(structure)
all[up] = '('
all[down] = ')'
print ''.join(all)
if not pairlist[up] == down:
print structure
raise Exception, "Failed to find partner in pairlist"
if not self._check_rule_match(rule, pairlist, positions):
return False
#if we got here, all the modules matched and all the rules were OK
return True
class SequenceEmbedder(object):
"""Generates and analyzes set of modules embedded inside longer sequence."""
def __init__(self, length, num_to_do, motif, model, composition, GU=True,\
with_replacement=False, positions=None, primer_5='',
primer_3='', match_offsets=None, debug=False, report_seqs=False
):
"""Initializes with a specified length sequence model, composition.
Note that sampling with replacement does NOT give all the outcomes
equal frequencies, e.g. with two choices (0,1) will happen half the
time because there are 2 ways to get it, but only one way to get
(0,0) or (1,1).
"""
self.Model = model
self.Motif = motif
self.NumToDo = long(num_to_do)
self.Length = long(length)
self.WithReplacement = with_replacement #allows adjacent modules
self.GU = GU
self.RandomRegion = UnpairedRegion('N'*(length - len(self.Model)), \
composition)
self.Composition = composition
self._fixed_positions = positions
self.Positions = positions
self.Primer3 = primer_3
self.Primer5 = primer_5
self.MatchOffsets = match_offsets
self.Debug = debug
self.ReportSeqs = report_seqs
def _get_composition(self):
"""Accessor for self.Composition."""
return self._composition
def _set_composition(self, composition):
"""Mutator for self.Composition."""
self._composition = composition
if composition:
self.Model.GU = self.GU
self.Model.Composition = composition
self.RandomRegion.Composition = composition
Composition = property(_get_composition, _set_composition)
def _choose_locations(self):
"""Picks out places for the modules."""
random_positions = self.Length - len(self.Model)
num_modules = len(self.Motif.Modules)
locations = []
with_replacement = self.WithReplacement
if (not with_replacement) and (random_positions < num_modules):
raise ValueError, "Not enough positions to place modules."
while len(locations) < num_modules:
if with_replacement:
curr = randrange(random_positions + 1)
locations.append(curr)
else:
curr = randrange(random_positions)
if curr not in locations:
locations.append(curr)
locations.sort()
return locations
def __str__(self):
"""Makes a new sequence with inserts at correct positions.
Note: no longer mutates self.Positions.
"""
pieces = [str(self.Primer5)]
random = str(self.RandomRegion.Current)
modules = list(self.Model)
added_positions = 0
last_position = 0
positions = self.Positions[:]
for i in range(len(positions)):
curr_module = modules[i]
curr_position = positions[i]
pieces.append(random[last_position:curr_position])
pieces.append(curr_module)
last_position = curr_position
positions[i] += added_positions
added_positions += len(curr_module)
pieces.append(random[last_position:]) #add anything left over
pieces.append(str(self.Primer3))
return ''.join(pieces)
def refresh(self):
"""Generates a new version of each module, incl. the random region."""
self.RandomRegion.refresh()
self.Model.GU = self.GU
self.Model.refresh()
def countMatches(self, verbose=False, temp=25):
"""Generates NumToDo sequences, folds them, and returns match count."""
positions = []
seqs = []
structs = []
orig_positions = self._fixed_positions
self.Positions = orig_positions
for i in xrange(self.NumToDo):
self.refresh()
if not orig_positions:
self.Positions = self._choose_locations()
curr_seq = str(self)
#adjust positions to account for inserted modules
curr_positions = self.Positions[:]
insert_length = len(self.Primer5)
module_lengths = map(len, list(self.Model))
for i in range(len(curr_positions)):
curr_positions[i] += insert_length
insert_length += module_lengths[i]
positions.append(curr_positions)
seqs.append(curr_seq)
folder = RNAfold(params={'-T':temp})
struct_file = folder(seqs)['StdOut']
odd = False
for line in struct_file:
if odd:
structs.append(ViennaStructure(line.split()[0]))
odd = not odd
good_count = 0
if self.Debug:
print "DEBUGGING" #debug code: prints seqs, structs, matches
for seq, struct, position in zip(seqs, structs, positions):
matched = self.Motif.structureMatches(struct, position, \
self.MatchOffsets,debug=self.Debug)
if matched:
good_count += 1
if self.Debug or (matched and self.ReportSeqs):
module_lengths = map(len, list(self.Model))
if self.Debug:
print "Module lengths:", module_lengths
print "Positions:", position
print seq
print struct
temp = [' '] * len(seq)
for l, p in zip(module_lengths, position):
temp[p:p+l] = ['*']*l
print ''.join(temp)
if self.Debug:
print "Offsets:", self.MatchOffsets
print matched
return good_count
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