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lists.py
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lists.py
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import collections
def partition(lst, f, save_keys = False):
"""partition(lst, f, save_keys = False) -> list
Partitions an iterable into sublists using a function to specify which
group they belong to.
It works by calling `f` on every element and saving the results into
an :class:`collections.OrderedDict`.
Arguments:
lst: The iterable to partition
f(function): The function to use as the partitioner.
save_keys(bool): Set this to True, if you want the OrderedDict
returned instead of just the values
Example:
>>> partition([1,2,3,4,5], lambda x: x&1)
[[1, 3, 5], [2, 4]]
"""
d = collections.OrderedDict()
for l in lst:
c = f(l)
s = d.setdefault(c, [])
s.append(l)
if save_keys:
return d
else:
return d.values()
def group(n, lst, underfull_action = 'ignore', fill_value = None):
"""group(n, lst, underfull_action = 'ignore', fill_value = None) -> list
Split sequence into subsequences of given size. If the values cannot be
evenly distributed among into groups, then the last group will either be
returned as is, thrown out or padded with the value specified in fill_value.
Arguments:
n (int): The size of resulting groups
lst: The list, tuple or string to group
underfull_action (str): The action to take in case of an underfull group at the end. Possible values are 'ignore', 'drop' or 'fill'.
fill_value: The value to fill into an underfull remaining group.
Returns:
A list containing the grouped values.
Example:
>>> group(3, "ABCDEFG")
['ABC', 'DEF', 'G']
>>> group(3, 'ABCDEFG', 'drop')
['ABC', 'DEF']
>>> group(3, 'ABCDEFG', 'fill', 'Z')
['ABC', 'DEF', 'GZZ']
>>> group(3, list('ABCDEFG'), 'fill')
[['A', 'B', 'C'], ['D', 'E', 'F'], ['G', None, None]]
"""
if underfull_action not in ['ignore', 'drop', 'fill']:
raise ValueError("group(): underfull_action must be either 'ignore', 'drop' or 'fill'")
if underfull_action == 'fill':
if isinstance(lst, tuple):
fill_value = (fill_value,)
elif isinstance(lst, list):
fill_value = [fill_value]
elif isinstance(lst, (str, unicode)):
if not isinstance(fill_value, (str, unicode)):
raise ValueError("group(): cannot fill a string with a non-string")
else:
raise ValueError("group(): 'lst' must be either a tuple, list or string")
out = []
for i in range(0, len(lst), n):
out.append(lst[i:i+n])
if out and len(out[-1]) < n:
if underfull_action == 'ignore':
pass
elif underfull_action == 'drop':
out.pop()
else:
out[-1] = out[-1] + fill_value * (n - len(out[-1]))
return out
def concat(l):
"""concat(l) -> list
Concats a list of lists into a list.
Example:
>>> concat([[1, 2], [3]])
[1, 2, 3]
"""
res = []
for k in l:
res.extend(k)
return res
def concat_all(*args):
"""concat_all(*args) -> list
Concats all the arguments together.
Example:
>>> concat_all(0, [1, (2, 3)], [([[4, 5, 6]])])
[0, 1, 2, 3, 4, 5, 6]
"""
if len(args) != 1:
return concat_all(list(args))
if not isinstance(args[0], (tuple, list)):
return [args[0]]
res = []
for k in args[0]:
res.extend(concat_all(k))
return res
def ordlist(s):
"""ordlist(s) -> list
Turns a string into a list of the corresponding ascii values.
Example:
>>> ordlist("hello")
[104, 101, 108, 108, 111]
"""
return map(ord, s)
def unordlist(cs):
"""unordlist(cs) -> str
Takes a list of ascii values and returns the corresponding string.
Example:
>>> unordlist([104, 101, 108, 108, 111])
'hello'
"""
return ''.join(chr(c) for c in cs)
def findall(haystack, needle):
"""findall(l, e) -> l
Generate all indices of needle in haystack, using the
Knuth-Morris-Pratt algorithm.
Example:
>>> foo = findall([1,2,3,4,4,3,4,2,1], 4)
>>> foo.next()
3
>>> foo.next()
4
>>> foo.next()
6
"""
def __kmp_table(W):
pos = 1
cnd = 0
T = []
T.append(-1)
T.append(0)
while pos < len(W):
if W[pos] == W[cnd]:
cnd += 1
pos += 1
T.append(cnd)
elif cnd > 0:
cnd = T[cnd]
else:
pos += 1
T.append(0)
return T
def __kmp_search(S, W):
m = 0
i = 0
T = __kmp_table(W)
while m + i < len(S):
if S[m + i] == W[i]:
i += 1
if i == len(W):
yield m
m += i - T[i]
i = max(T[i], 0)
else:
m += i - T[i]
i = max(T[i], 0)
def __single_search(S, w):
for i in xrange(len(S)):
if S[i] == w:
yield i
if type(haystack) != type(needle):
needle = [needle]
if len(needle) == 1:
return __single_search(haystack, needle[0])
else:
return __kmp_search(haystack, needle)