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# encoding: utf-8
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"""Utilities for working with data structures like lists, dicts and tuples.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2008-2009 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-----------------------------------------------------------------------------
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import types
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#-----------------------------------------------------------------------------
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# Code
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#-----------------------------------------------------------------------------
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def uniq_stable(elems):
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"""uniq_stable(elems) -> list
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Return from an iterable, a list of all the unique elements in the input,
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but maintaining the order in which they first appear.
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A naive solution to this problem which just makes a dictionary with the
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elements as keys fails to respect the stability condition, since
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dictionaries are unsorted by nature.
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Note: All elements in the input must be valid dictionary keys for this
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routine to work, as it internally uses a dictionary for efficiency
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reasons."""
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unique = []
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unique_dict = {}
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for nn in elems:
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if nn not in unique_dict:
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unique.append(nn)
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unique_dict[nn] = None
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return unique
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def sort_compare(lst1, lst2, inplace=1):
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"""Sort and compare two lists.
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By default it does it in place, thus modifying the lists. Use inplace = 0
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to avoid that (at the cost of temporary copy creation)."""
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if not inplace:
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lst1 = lst1[:]
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lst2 = lst2[:]
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lst1.sort(); lst2.sort()
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return lst1 == lst2
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def list2dict(lst):
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"""Takes a list of (key,value) pairs and turns it into a dict."""
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dic = {}
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for k,v in lst: dic[k] = v
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return dic
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def list2dict2(lst, default=''):
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"""Takes a list and turns it into a dict.
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Much slower than list2dict, but more versatile. This version can take
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lists with sublists of arbitrary length (including sclars)."""
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dic = {}
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for elem in lst:
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if type(elem) in (types.ListType,types.TupleType):
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size = len(elem)
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if size == 0:
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pass
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elif size == 1:
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dic[elem] = default
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else:
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k,v = elem[0], elem[1:]
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if len(v) == 1: v = v[0]
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dic[k] = v
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else:
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dic[elem] = default
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return dic
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def flatten(seq):
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"""Flatten a list of lists (NOT recursive, only works for 2d lists)."""
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return [x for subseq in seq for x in subseq]
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def get_slice(seq, start=0, stop=None, step=1):
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"""Get a slice of a sequence with variable step. Specify start,stop,step."""
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if stop == None:
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stop = len(seq)
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item = lambda i: seq[i]
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return map(item,xrange(start,stop,step))
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def chop(seq, size):
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"""Chop a sequence into chunks of the given size."""
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chunk = lambda i: seq[i:i+size]
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return map(chunk,xrange(0,len(seq),size))
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