在python中查找字符串中的大小写字母数

def count_letters(s):
    upper_count = 0
    lower_count = 0
    for char in s:
        if char.isupper():
            upper_count += 1
        elif char.islower():
            lower_count += 1
    return upper_count, lower_count

# 示例字符串
test_string = "Hello World! 123"
upper_count, lower_count = count_letters(test_string)

print(f"大写字母数: {upper_count}")
print(f"小写字母数: {lower_count}")

def count_letters(s):
    upper_count = 0
    lower_count = 0
    for char in s:
        if char.isalpha():
            if char.isupper():
                upper_count += 1
            elif char.islower():
                lower_count += 1
    return upper_count, lower_count

def count_letters(s):
    if not s:
        return "输入字符串为空"
    upper_count = 0
    lower_count = 0
    for char in s:
        if char.isalpha():
            if char.isupper():
                upper_count += 1
            elif char.islower():
                lower_count += 1
    return upper_count, lower_count