如何使用Python 2检查一个字符串中是否有几个特定的字符?
例如,给定以下字符串:
这些罪犯偷走了价值一百万美元的珠宝。
如何检测它是否有美元符号("$")、逗号(",")和数字?
发布于 2011-03-04 10:07:17
假设您的字符串为s
'$' in s # found
'$' not in s # not found
# original answer given, but less Pythonic than the above...
s.find('$')==-1 # not found
s.find('$')!=-1 # found
对于其他角色,依此类推。
..。或
pattern = re.compile(r'\d\$,')
if pattern.findall(s):
print('Found')
else
print('Not found')
..。或
chars = set('0123456789$,')
if any((c in chars) for c in s):
print('Found')
else:
print('Not Found')
编辑:添加了'$' in s
答案
发布于 2011-03-04 10:39:10
用户Jochen Ritzel在评论中回答了用户dappawit的这个问题。它应该是有效的:
('1' in var) and ('2' in var) and ('3' in var) ...
“%1”、“%2”等应替换为您要查找的字符。
有关字符串的一些信息,请参见this page in the Python 2.7 documentation,包括使用in
运算符进行子字符串测试。
更新:这与我上面的建议做得一样,重复的次数更少:
# When looking for single characters, this checks for any of the characters...
# ...since strings are collections of characters
any(i in '<string>' for i in '123')
# any(i in 'a' for i in '123') -> False
# any(i in 'b3' for i in '123') -> True
# And when looking for subsrings
any(i in '<string>' for i in ('11','22','33'))
# any(i in 'hello' for i in ('18','36','613')) -> False
# any(i in '613 mitzvahs' for i in ('18','36','613')) ->True
发布于 2015-07-15 01:11:38
Abbafei回复帖子的时间快速比较:
import timeit
def func1():
phrase = 'Lucky Dog'
return any(i in 'LD' for i in phrase)
def func2():
phrase = 'Lucky Dog'
if ('L' in phrase) or ('D' in phrase):
return True
else:
return False
if __name__ == '__main__':
func1_time = timeit.timeit(func1, number=100000)
func2_time = timeit.timeit(func2, number=100000)
print('Func1 Time: {0}\nFunc2 Time: {1}'.format(func1_time, func2_time))
输出:
Func1 Time: 0.0737484362111
Func2 Time: 0.0125144964371
因此,使用any的代码更紧凑,但使用条件的代码更快。
EDIT : TL;DR --对于长字符串,if-then仍然比任何字符串都快!
我决定根据评论中提出的一些有效观点来比较长随机字符串的时间:
# Tested in Python 2.7.14
import timeit
from string import ascii_letters
from random import choice
def create_random_string(length=1000):
random_list = [choice(ascii_letters) for x in range(length)]
return ''.join(random_list)
def function_using_any(phrase):
return any(i in 'LD' for i in phrase)
def function_using_if_then(phrase):
if ('L' in phrase) or ('D' in phrase):
return True
else:
return False
if __name__ == '__main__':
random_string = create_random_string(length=2000)
func1_time = timeit.timeit(stmt="function_using_any(random_string)",
setup="from __main__ import function_using_any, random_string",
number=200000)
func2_time = timeit.timeit(stmt="function_using_if_then(random_string)",
setup="from __main__ import function_using_if_then, random_string",
number=200000)
print('Time for function using any: {0}\nTime for function using if-then: {1}'.format(func1_time, func2_time))
输出:
Time for function using any: 0.1342546
Time for function using if-then: 0.0201827
If-then几乎比任何一个都快一个数量级!
https://stackoverflow.com/questions/5188792
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