计算字符串中某个字符出现的次数

如何计算字符串中字符出现的次数?

如。“a”在“Mary had a little lamb”中出现了4次。

当前回答

myString.count('a');

更多信息请点击这里

其他回答

Str.count (sub[， start[， end]]) 返回子字符串sub在范围[start, end]中不重叠出现的次数。可选参数start和end被解释为片表示法。

>>> sentence = 'Mary had a little lamb'
>>> sentence.count('a')
4

Python 3

有两种方法可以做到这一点:

1)内置函数count()

sentence = 'Mary had a little lamb'
print(sentence.count('a'))`

2)不使用函数

sentence = 'Mary had a little lamb'    
count = 0

for i in sentence:
    if i == "a":
        count = count + 1

print(count)

正则表达式?

import re
my_string = "Mary had a little lamb"
len(re.findall("a", my_string))

要获得所有字母的计数，请使用集合。计数器:

>>> from collections import Counter
>>> counter = Counter("Mary had a little lamb")
>>> counter['a']
4

a = 'have a nice day'
symbol = 'abcdefghijklmnopqrstuvwxyz'
for key in symbol:
    print(key, a.count(key))

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