如何检查字符串是否有特定的字母？

string = "Hello World"
if 'o' in string:
    print("字符串中包含字母'o'")
else:
    print("字符串中不包含字母'o'")

import re

string = "Hello World"
pattern = r'o'
if re.search(pattern, string):
    print("字符串中包含字母'o'")
else:
    print("字符串中不包含字母'o'")

string = "Hello World"
target_letter = 'o'
found = False

for letter in string:
    if letter == target_letter:
        found = True
        break

if found:
    print("字符串中包含字母'o'")
else:
    print("字符串中不包含字母'o'")