如何合併列表中的項目

Question

我在Python中列表有問題。當我打印「列表」我有這樣的結果：

[1,2,3] 
[4,5,6] 

所以我有兩個列表中的一個變量我猜。我怎樣才能將這些項目合併到一個變量？

Answer 1

試試這個，

>>> a 
[[1, 2, 3], [4, 5, 6]] 
>>> result=[] 
>>> for i in a: 
    result+=i 


>>> result 
[1, 2, 3, 4, 5, 6] 
>>> 

OR

>>> a 
[[1, 2, 3], [4, 5, 6]] 
>>> sum(a, []) 

輸出：

[1, 2, 3, 4, 5, 6] 

OR

>>> a1 
[1, 2, 3] 
>>> a2 
[4, 5, 6] 
>>> [item for item in itertools.chain(a1, a2)] 

輸出：

[1, 2, 3, 4, 5, 6] 

Answer 2

如果：

returnList = [[1,2,3], [4,5,6]] 

你可以很容易做到：

>>> returnList = [j for i in returnList for j in i] 

或者：

>>> returnList = [j for i in returnList for j in i] 

或者，你也可以這樣做：

>>> returnList = reduce(lambda i,j: i+j, returnList) 

雙方將返回：[1, 2, 3, 4, 5, 6]

Answer 3

我會做，使用itertools.chain：

>>> import itertools 
>>> a = [[1, 2, 3], [4 , 5, 6]] 
>>> a = itertools.chain.from_iterable(a) 
>>> a 
[1, 2, 3, 4, 5, 6] 

Answer 4

l = [['0', '1', '2'], ['3', '4', '5']] 

def merge_list(l): 
    temp = [] 
    for i in l: 
     for j in i: 
      temp.append(j) 
    return temp 

print merge_list(l) 

結果

['0', '1', '2', '3', '4', '5'] 

Answer 5

Merge 2 list in python

listtwo = [8,9,0] 
listone = [1,2,3,4,5] 
mergedlist = listone + listtwo 

Answer 6

這裏我收集了一些解決方案，只是嘗試timeit：

這裏是我的代碼片段：

#!/usr/bin/python 

def f1(List): 
    x = [] 
    [ x.extend(y) for y in List ] 
    return x 

def f2(List): 
    return sum(List, []) 

def f3(List): 
    temp = [] 
    for i in List: 
     for j in i: 
      temp.append(j) 
    return temp 

def f4(List): 
    result=[] 
    for i in List: 
     result += i 
    return result 

def f5(List): 
    return [j for i in List for j in i] 

import cProfile 
import itertools 
from faker import Faker 
from timeit import Timer 

s = Faker() 
# instead of faker you can use random module 
func = [ f1, f2, f3, f4, f5, f6 ] 
Lis = [[ s.random_int(min=1, max=99) 
     for x in range(1000) ] 
     for x in range(100)] 

for fun in func: 
    t = Timer(lambda: fun(Lis)) 
    print fun.__name__, cProfile.run('t.timeit(number=1000)') 

輸出：

f1   102011 function calls in 0.701 seconds 

    Ordered by: standard name 

    ncalls tottime percall cumtime percall filename:lineno(function) 
     1 0.000 0.000 0.701 0.701 <string>:1(<module>) 
    1000 0.040 0.000 0.495 0.000 merge.py:3(f1) 
    1000 0.001 0.000 0.495 0.000 merge.py:42(<lambda>) 
     1 0.000 0.000 0.000 0.000 timeit.py:143(setup) 
     1 0.000 0.000 0.701 0.701 timeit.py:178(timeit) 
     1 0.206 0.206 0.701 0.701 timeit.py:96(inner) 
     1 0.000 0.000 0.000 0.000 {gc.disable} 
     1 0.000 0.000 0.000 0.000 {gc.enable} 
     1 0.000 0.000 0.000 0.000 {gc.isenabled} 
     1 0.000 0.000 0.000 0.000 {globals} 
     1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 
    100000 0.455 0.000 0.455 0.000 {method 'extend' of 'list' objects} 
     2 0.000 0.000 0.000 0.000 {time.time} 


None 
f2   3011 function calls in 37.747 seconds 

    Ordered by: standard name 

    ncalls tottime percall cumtime percall filename:lineno(function) 
     1 0.000 0.000 37.747 37.747 <string>:1(<module>) 
    1000 0.003 0.000 37.418 0.037 merge.py:42(<lambda>) 
    1000 0.004 0.000 37.415 0.037 merge.py:8(f2) 
     1 0.000 0.000 0.000 0.000 timeit.py:143(setup) 
     1 0.000 0.000 37.747 37.747 timeit.py:178(timeit) 
     1 0.329 0.329 37.747 37.747 timeit.py:96(inner) 
     1 0.000 0.000 0.000 0.000 {gc.disable} 
     1 0.000 0.000 0.000 0.000 {gc.enable} 
     1 0.000 0.000 0.000 0.000 {gc.isenabled} 
     1 0.000 0.000 0.000 0.000 {globals} 
     1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 
    1000 37.411 0.037 37.411 0.037 {sum} 
     2 0.000 0.000 0.000 0.000 {time.time} 


None 
f3   100002011 function calls in 28.044 seconds 

    Ordered by: standard name 

    ncalls tottime percall cumtime percall filename:lineno(function) 
     1 0.000 0.000 28.044 28.044 <string>:1(<module>) 
    1000 20.304 0.020 27.676 0.028 merge.py:11(f3) 
    1000 0.001 0.000 27.677 0.028 merge.py:42(<lambda>) 
     1 0.000 0.000 0.000 0.000 timeit.py:143(setup) 
     1 0.000 0.000 28.044 28.044 timeit.py:178(timeit) 
     1 0.367 0.367 28.044 28.044 timeit.py:96(inner) 
     1 0.000 0.000 0.000 0.000 {gc.disable} 
     1 0.000 0.000 0.000 0.000 {gc.enable} 
     1 0.000 0.000 0.000 0.000 {gc.isenabled} 
     1 0.000 0.000 0.000 0.000 {globals} 
100000000 7.372 0.000 7.372 0.000 {method 'append' of 'list' objects} 
     1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 
     2 0.000 0.000 0.000 0.000 {time.time} 


None 
f4   2011 function calls in 0.826 seconds 

    Ordered by: standard name 

    ncalls tottime percall cumtime percall filename:lineno(function) 
     1 0.000 0.000 0.826 0.826 <string>:1(<module>) 
    1000 0.463 0.000 0.463 0.000 merge.py:18(f4) 
    1000 0.001 0.000 0.464 0.000 merge.py:42(<lambda>) 
     1 0.000 0.000 0.000 0.000 timeit.py:143(setup) 
     1 0.000 0.000 0.826 0.826 timeit.py:178(timeit) 
     1 0.362 0.362 0.826 0.826 timeit.py:96(inner) 
     1 0.000 0.000 0.000 0.000 {gc.disable} 
     1 0.000 0.000 0.000 0.000 {gc.enable} 
     1 0.000 0.000 0.000 0.000 {gc.isenabled} 
     1 0.000 0.000 0.000 0.000 {globals} 
     1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 
     2 0.000 0.000 0.000 0.000 {time.time} 


None 
f5   2011 function calls in 4.608 seconds 

    Ordered by: standard name 

    ncalls tottime percall cumtime percall filename:lineno(function) 
     1 0.000 0.000 4.608 4.608 <string>:1(<module>) 
    1000 4.253 0.004 4.253 0.004 merge.py:24(f5) 
    1000 0.001 0.000 4.254 0.004 merge.py:42(<lambda>) 
     1 0.000 0.000 0.000 0.000 timeit.py:143(setup) 
     1 0.000 0.000 4.608 4.608 timeit.py:178(timeit) 
     1 0.354 0.354 4.608 4.608 timeit.py:96(inner) 
     1 0.000 0.000 0.000 0.000 {gc.disable} 
     1 0.000 0.000 0.000 0.000 {gc.enable} 
     1 0.000 0.000 0.000 0.000 {gc.isenabled} 
     1 0.000 0.000 0.000 0.000 {globals} 
     1 0.000 0.000 0.000 0.000 {method 'disable' of '_lsprof.Profiler' objects} 
     2 0.000 0.000 0.000 0.000 {time.time} 


None