如何檢查字符串中的特定字符？

Question

如何使用 Python 2 檢查字符串中是否包含多個特定字符？

例如，給定以下字符串：

犯罪分子偷走了價值 1,000,000 美元的珠寶。

如何檢測它是否有美元符號 ("$")、逗號 (",") 和數字？

Answer 1

假設你的字符串是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

其他角色依此類推。

... 或者

pattern = re.compile(r'\d\$,')
if pattern.findall(s):
    print('Found')
else
    print('Not found')

... 或者

chars = set('0123456789$,')
if any((c in chars) for c in s):
    print('Found')
else:
    print('Not Found')

[編輯： '$' in s答案中添加了'$' in s ]

Answer 2

用戶 Jochen Ritzel 在評論用戶 dappawit 對此問題的回答時說到。 它應該工作：

('1' in var) and ('2' in var) and ('3' in var) ...

'1'、'2' 等應替換為您要查找的字符。

有關字符串的一些信息，包括有關使用in運算符進行子字符串測試的信息，請參閱Python 2.7 文檔中的此頁面。

更新：這與我上面的建議做同樣的工作，但重復次數更少：

# 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

Answer 3

響應 Abbafei 帖子的時間快速比較：

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))

輸出：

Func1 Time: 0.0737484362111
Func2 Time: 0.0125144964371

所以代碼更緊湊，但條件更快。

---

編輯： TL;DR-對於長字符串，if-then仍然比任何字符串都快！

我決定根據評論中提出的一些有效觀點來比較長隨機字符串的時間：

# 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))

輸出：

Time for function using any: 0.1342546
Time for function using if-then: 0.0201827

如果-那么幾乎比任何一個都快一個數量級！

Answer 4

這將測試字符串是否由某些組合或數字、美元符號和逗號組成。 這就是你要找的嗎？

import re

s1 = 'Testing string'
s2 = '1234,12345$'

regex = re.compile('[0-9,$]+$')

if ( regex.match(s1) ):
   print "s1 matched"
else:
   print "s1 didn't match"

if ( regex.match(s2) ):
   print "s2 matched"
else:
   print "s2 didn't match"

Answer 5

我的簡單，簡單，簡單的方法！ =D

代碼

string_to_test = "The criminals stole $1,000,000 in jewels."
chars_to_check = ["$", ",", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
for char in chars_to_check:
    if char in string_to_test:
        print("Char \"" + char + "\" detected!")

輸出

Char "$" detected!
Char "," detected!
Char "0" detected!
Char "1" detected!

謝謝！

Answer 6

檢查字符是否在字符串中：

parse_string = lambda chars, string: [char in string for char in chars]

例子：

parse_string('$,x', 'The criminals stole $1,000,000 in ....') 

或者

parse_string(['$', ',', 'x'], '..minals stole $1,000,000 i..')

輸出： [True, True, False]

Answer 7

s=input("Enter any character:")   
if s.isalnum():   
   print("Alpha Numeric Character")   
   if s.isalpha():   
       print("Alphabet character")   
       if s.islower():   
         print("Lower case alphabet character")   
       else:   
         print("Upper case alphabet character")   
   else:   
     print("it is a digit")   
elif s.isspace():   
    print("It is space character")   

別的：
print("非空格特殊字符")