python - Pythonで、az、AZ、0-9、_、および-を除くすべての文字を文字列から削除する最も効率的な方法は何ですか？

Question

注意：最大文字列は15文字になります。

Answer 1

ここで生の速度を比較するために、@ wimの答え、そのいくつかの最適化、および正規表現ソリューションの比較を示します。

import re, string, timeit

clean = re.compile(r'[^a-zA-Z0-9_-]')
keep = string.ascii_letters + string.digits + '_-'
keep_set = set(string.ascii_letters + string.digits + '_-')
test = '$pam and_Eggs##-!'
cur_encoding_bytes = 256 # 8 for UTF-8, in Python 3 this would be different for Unicode
all_else = ''.join(chr(i) for i in range(cur_encoding_bytes) if chr(i) not in keep_set) # taken from https://stackoverflow.com/a/3588485/1219006

def clean1(s):
    return ''.join(x for x in s if x in keep)

def clean1_filter(s):
    return filter(keep.__contains__, s)

def clean1_filter_set(s):
    return filter(keep_set.__contains__, s)

def clean2(s):
    return clean.sub('', s)

def clean3(s):
    return s.translate(None, all_else)

print timeit.timeit('clean1(test)', 'from __main__ import clean1, test')
print timeit.timeit('clean1_filter(test)', 'from __main__ import clean1_filter, test')
print timeit.timeit('clean1_filter_set(test)', 'from __main__ import clean1_filter_set, test')
print timeit.timeit('clean2(test)', 'from __main__ import clean2, test')
print timeit.timeit('clean3(test)', 'from __main__ import clean3, test')

このスクリプトの出力は次のとおりです。

2.96962522809
1.56208783165
1.10597814849
1.59298783663
0.53834820236

str.translateは最速で、特殊な文字列メソッドです。

Answer 2

>>> def clean(s):
...   from string import ascii_letters, digits
...   keep = ascii_letters + digits + '_-'
...   return ''.join(x for x in s if x in keep)
... 
>>> clean('$pam and_Eggs##-!')
'pamand_Eggs-'