Question

在删除字符串之前检查子字符串（在我的情况下是一个空格）是否更快，或者在全局使用relace()时，是否更快;

用例：

a = ['452 04','45204','455 04','88804']
for i,e in enumerate(a):
    if re.search(r"\s", e):
       a[i] = e.replace(' ','')

也欢迎任何其他建议。

Answer 1

import re

def with_re_search():
    a = ['452 04','45204','455 04','88804']
    for i,e in enumerate(a):
        if re.search(r"\s", e):
            a[i] = e.replace(' ','')

def with_in():
    a = ['452 04','45204','455 04','88804']
    for i,e in enumerate(a):
        if ' ' in e:
            a[i] = e.replace(' ','')

def without_search():
    a = ['452 04','45204','455 04','88804']
    for i,e in enumerate(a):
        a[i] = e.replace(' ','')

def with_translate():
    a = ['452 04','45204','455 04','88804']
    for i, e in enumerate(a):
        a[i] = e.translate(None,'')

from timeit import timeit as t
n = 1000000
t('f()', setup='from __main__ import with_re_search as f', number=n) # 5.37417006493
t('f()', setup='from __main__ import with_in as f',        number=n) # 1.04646992683
t('f()', setup='from __main__ import without_search as f', number=n) # 1.2475438118
t('f()', setup='from __main__ import with_translate as f', number=n) # 1.56214690208

使用re.search绝对比其他选项慢。

这是在CPython 2.7.3，Ubuntu Linux 12.10 64bit中完成的。

UPDATE ：在CPython 3.3.0（同一台机器）中。

t('f()', setup='from __main__ import with_re_search as f', number=n) # 24.345079875027295
t('f()', setup='from __main__ import with_in as f',        number=n) # 1.1399168980424292
t('f()', setup='from __main__ import without_search as f', number=n) # 1.3967725560069084

注意无法计时str.translate，因为Python 3中的str.translate不接受deletechars参数。

Answer 2

如果您所说的只是删除空格，可以使用translate。

a = ['452 04','45204','455 04','88804']
a = [item.translate(None, " ") for item in a]
print a

在删除子字符串之前检查子字符串是否更快？

2 个答案: