Kelly Bundy

代替 let transformed = transform(el) 具有 for transformed in [transform(el)] .

更多变化:

from itertools import cycle
from operator import add

A = ['A','B','C','D','E','F','G','H']
B = ['a','b']
E = ['Aa','Bb','Ca','Db','Ea','Fb','Ga','Hb']

C = list(map(add, A, cycle(B)))
print(C == E)

C = [a + B[i%2] for i, a in enumerate(A)]
print(C == E)

C = list(map(''.join, zip(A, cycle(B))))
print(C == E)

C = list(map('{}{}'.format, A, cycle(B)))
print(C == E)

您可以使用二进制搜索来查找开关索引:

from bisect import bisect_left
switchIndex = bisect_left(list1, switchValue)

然后在不使用Python循环的情况下打印(哦,在Python 2中不起作用,但下面的另一个可以):

print(*list1[:switchIndex], sep='\n')
print(*list2, sep='\n')

或者:

print('\n'.join(map(str, list1[:switchIndex])))
print('\n'.join(map(str, list2)))

在Python 2中,在10万倍长的列表上与您和deceze的列表一起进行基准测试:

 51 ms   52 ms   52 ms  Kelly2
137 ms  138 ms  138 ms  original
138 ms  138 ms  138 ms  deceze1
160 ms  160 ms  161 ms  deceze2
164 ms  164 ms  165 ms  deceze3

在Python 3中:

111 ms  114 ms  114 ms  Kelly2
134 ms  134 ms  135 ms  Kelly1
176 ms  177 ms  178 ms  deceze1
178 ms  178 ms  178 ms  original
189 ms  189 ms  191 ms  deceze2
191 ms  192 ms  192 ms  deceze3

(不包括@buhtz's,因为它不太具有可比性。)

基准代码( Try it online! - Python 2 version ):

def original():
    for i in list1:
        if i < switchValue:
            print(i)
        else:
            for j in list2:
                print(j)
            break

def deceze1():
    for i in list1:
        if i >= switchValue:
            break
        print(i)
    for i in list2:
        print(i)

def deceze2():
    for i in takewhile(lambda i: i < switchValue, list1):
        print(i)
    for i in list2:
        print(i)

def deceze3():
    for i in chain(takewhile(lambda i: i < switchValue, list1), list2):
        print(i)

def Kelly1():
    switchIndex = bisect_left(list1, switchValue)
    print(*list1[:switchIndex], sep='\n')
    print(*list2, sep='\n')

def Kelly2():
    switchIndex = bisect_left(list1, switchValue)
    print('\n'.join(map(str, list1[:switchIndex])))
    print('\n'.join(map(str, list2)))

funcs = original, deceze1, deceze2, deceze3, Kelly1, Kelly2

import os, sys
from timeit import default_timer as timer
from bisect import bisect_left
from itertools import takewhile, chain

list1 = [1, 3, 5, 8]
list2 = [7, 10, 12]
switchValue = 4

for func in funcs:
    print(func.__name__ + ':')
    func()

n = 100_000
list1 = [x for x in list1 for _ in range(n)]
list2 = [x for x in list2 for _ in range(n)]

print('benchmark:')
tss = [[] for _ in funcs]
for _ in range(10):
    for func, ts in zip(funcs, tss):
        with open(os.devnull, 'w') as sys.stdout:
            t0 = timer()
            func()
            t1 = timer()
        sys.stdout = sys.__stdout__
        ts.append(t1 - t0)
        ts.sort()
for func, ts in sorted(zip(funcs, tss), key=lambda x: x[1]):
    print(*('%d ms ' % (t * 1e3) for t in sorted(ts)[:3]), func.__name__)