Python字符串中出现的次数统计多种方法

def count_substring(main_string, substring):
    return main_string.count(substring)

main_string = "Hello, hello, hello, world!"
substring = "hello"
print(count_substring(main_string, substring))  # 输出：3

import re

def count_substring_regex(main_string, substring):
    pattern = re.compile(substring)
    return len(re.findall(pattern, main_string))

main_string = "Hello, hello123, hello, world!"
substring = "hello"
print(count_substring_regex(main_string, substring))  # 输出：2（注意：这里只匹配了"hello"，没有匹配"hello123"）

def count_substring_list_comprehension(main_string, substring):
    return sum(1 for _ in range(len(main_string)) if main_string[_:_ + len(substring)] == substring)

main_string = "Hello, hello, hello, world!"
substring = "hello"
print(count_substring_list_comprehension(main_string, substring))  # 输出：3

def count_substring_loop(main_string, substring):
    count = 0
    start_index = 0
    while True:
        start_index = main_string.find(substring, start_index)
        if start_index == -1:
            break
        count += 1
        start_index += len(substring)
    return count

main_string = "Hello, hello, hello, world!"
substring = "hello"
print(count_substring_loop(main_string, substring))  # 输出：3

def count_substring_split(main_string, delimiter):
    return len(main_string.split(delimiter)) - 1

main_string = "apple,banana,apple,orange"
delimiter = "apple"
print(count_substring_split(main_string, delimiter))  # 输出：2