在Python中复制数组/列表的有效方法

使用

timeit

from copy import *a=range(1000)def cop():    b=copy(a)def func1():    b=list(a)def slice():    b=a[:]def slice_len():    b=a[0:len(a)]if __name__=="__main__":    import timeit    print "copy(a)",timeit.timeit("cop()", setup="from __main__ import cop")    print "list(a)",timeit.timeit("func1()", setup="from __main__ import func1")    print "a[:]",timeit.timeit("slice()", setup="from __main__ import slice")    print "a[0:len(a)]",timeit.timeit("slice_len()", setup="from __main__ import slice_len")

结果：

copy(a) 3.98940896988list(a) 2.54542589188a[:] 1.96630120277        #winnera[0:len(a)] 10.5431251526

当然，其中涉及的额外步骤

a[0:len(a)]

这是两者的字节码比较：

In [19]: dis.dis(func1)  20 LOAD_GLOBAL   0 (range)   3 LOAD_ConST    1 (100000)   6 CALL_FUNCTION 1   9 STORE_FAST    0 (a)  3          12 LOAD_FAST     0 (a)  15 SLICE+0    16 STORE_FAST    1 (b)  19 LOAD_ConST    0 (None)  22 RETURN_VALUEIn [20]: dis.dis(func2)  20 LOAD_GLOBAL   0 (range)   3 LOAD_ConST    1 (100000)   6 CALL_FUNCTION 1   9 STORE_FAST    0 (a)  3          12 LOAD_FAST     0 (a)    #same up to here  15 LOAD_ConST    2 (0)    #loads 0  18 LOAD_GLOBAL   1 (len) # loads the builtin len(),     # so it might take some lookup time  21 LOAD_FAST     0 (a)  24 CALL_FUNCTION 127 SLICE+3    28 STORE_FAST    1 (b)  31 LOAD_ConST    0 (None)  34 RETURN_VALUE