Python - 删除所有非字母并用下划线替换它们的有效方法 [英] Python - efficient method to remove all non-letters and replace them with underscores

问题描述

def format_title(title):  
  ''.join(map(lambda x: x if (x.isupper() or x.islower()) else '_', title.strip()))

有什么更快的吗?

推荐答案

更快的方法是使用 str.translate()这比你的方式快约 50 倍

The faster way to do it is to use str.translate() This is ~50 times faster than your way

# You only need to do this once
>>> title_trans=''.join(chr(c) if chr(c).isupper() or chr(c).islower() else '_' for c in range(256))

>>> "abcde1234!@%^".translate(title_trans)
'abcde________'

# Using map+lambda
$ python -m timeit '"".join(map(lambda x: x if (x.isupper() or x.islower()) else "_", "abcd1234!@#$".strip()))'
10000 loops, best of 3: 21.9 usec per loop

# Using str.translate
$ python -m timeit -s 'titletrans="".join(chr(c) if chr(c).isupper() or chr(c).islower() else "_" for c in range(256))' '"abcd1234!@#$".translate(titletrans)'
1000000 loops, best of 3: 0.422 usec per loop

# Here is regex for a comparison
$ python -m timeit -s 'import re;transre=re.compile("[\W\d]+")' 'transre.sub("_","abcd1234!@#$")'
100000 loops, best of 3: 3.17 usec per loop

这是unicode的一个版本

Here is a version for unicode

# coding: UTF-8

def format_title_unicode_translate(title):
    return title.translate(title_unicode_trans)

class TitleUnicodeTranslate(dict):
    def __missing__(self,item):
        uni = unichr(item)
        res = u"_"
        if uni.isupper() or uni.islower():
            res = uni
        self[item] = res
        return res
title_unicode_trans=TitleUnicodeTranslate()

print format_title_unicode_translate(u"Metallica Μεταλλικα")

请注意，希腊字母算作大写和小写，因此不会被替换.如果要替换它们，只需将条件更改为

Note that the Greek letters count as upper and lower, so they are not substituted. If they are to be substituted, simply change the condition to

        if item<256 and (uni.isupper() or uni.islower()):

这篇关于Python - 删除所有非字母并用下划线替换它们的有效方法的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！