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  1. def join(a):
  2.     """Joins a sequence of sequences into a single sequence.  (One-level flattening.)
  3.     E.g., join([(1,2,3), [4, 5], [6, (7, 8, 9), 10]]) = [1,2,3,4,5,6,(7,8,9),10]
  4.     This is very efficient, especially when the subsequences are long.
  5.     """
  6.     n = sum([len(b) for b in a])
  7.     l = [None]*n
  8.     i = 0
  9.     for b in a:
  10.         j = i+len(b)
  11.         l[i:j] = b
  12.         i = j
  13.     return l
  14.  
  15. def join2(a):
  16.     result = []
  17.     for x in a:
  18.         result.extend(x)
  19.     return result
  20.  
  21. def join3(a):
  22.     result = []
  23.     map(result.extend, a)
  24.     return result
  25.  
  26. def join4(a):
  27.     return reduce(lambda l, r: l.extend(r) or l, a, [])
  28.  
  29. testdata = [range(t) for t in range(100, 200)]
  30.  
  31. import timeit, pprint
  32. results = [
  33.     (funcname, timeit.timeit(lambda: func(testdata), number=150))
  34.     for funcname, func in locals().items()
  35.     if hasattr(func, '__call__')]
  36. pprint.pprint(sorted(results, key=lambda x: x[1]))
Success #stdin #stdout 0.17s 10960KB
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Standard input is empty
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[('join3', 0.015027999877929688),
 ('join2', 0.01589202880859375),
 ('join4', 0.019412994384765625),
 ('join', 0.03456687927246094)]
https://ideone.com/9q3mrp
language:
Python (cpython 2.7.16)
created:
11 years ago
visibility:
public

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