s='wOrd'

[x for x in s if x==x.upper()]

['O']

''.join(x for x in s if x==x.upper())

'O'

更一般的情况：

s='My Name is John'

[x for x in s if x==x.upper() and x!=' ']

['M', 'N', 'J']

''.join(x for x in s if x==x.upper() and x!=' ')

'MNJ'

欢迎来到StackOverflow。
1是字母“O”的索引一旦你有了索引，你就可以简单地用它来打印或做其他任何事情。

test = "wOrd"
print(test[1])

上方将打印“O”

使用str.isupper方法：

s = "wOrd"

# print every upper-case character
print(*(char for char in s if char.isupper()))

# print every upper-case character - functional programming
print(''.join(filter(str.isupper, s)))

# print the 1st upper-case character. If none returns None
print(next((char for char in s if char.isupper()), None))