消除python中字符串中多次出现的空格

Question

如果我有一个字符串

"this is   a    string"

如何缩短它以使我在单词之间只有一个空格而不是多个空格？(空格的数量是随机的)

"this is a string"

Answer 1

您可以使用string.split并" ".join(list)以合理的pythonic方式实现这一点 - 可能有更高效的算法,但它们看起来不太好.

顺便说一句,这比使用正则表达式快得多,至少在示例字符串上:

import re
import timeit

s = "this    is   a     string"

def do_regex():
    for x in xrange(100000):
        a = re.sub(r'\s+', ' ', s)

def do_join():
    for x in xrange(100000):
        a = " ".join(s.split())


if __name__ == '__main__':
    t1 = timeit.Timer(do_regex).timeit(number=5)
    print "Regex: ", t1
    t2 = timeit.Timer(do_join).timeit(number=5)
    print "Join: ", t2


$ python revsjoin.py 
Regex:  2.70868492126
Join:  0.333452224731

编译这个正则表达式确实提高了性能,但是只有在调用sub已编译的正则表达式时,而不是将编译后的表单re.sub作为参数传递:

def do_regex_compile():
  pattern = re.compile(r'\s+')
  for x in xrange(100000):
    # Don't do this
    # a = re.sub(pattern, ' ', s)
    a = pattern.sub(' ', s)

$ python revsjoin.py  
Regex:  2.72924399376
Compiled Regex:  1.5852200985
Join:  0.33763718605

Answer 2

re.sub(r'\s+', ' ', 'this is   a    string')

您可以预编译并存储它,以获得更好的性能:

MULT_SPACES = re.compile(r'\s+')
MULT_SPACES.sub(' ', 'this is   a    string')