Python新手技术问询：如何实现判断字符串仅含数字5和6的numberCheck布尔函数

Hey there! No sweat—let's break this down nice and simple since you're new to Python. The goal is to write a function that checks if every character in the input string is either '5' or '6', right? Here's how to do it step by step.

Core Idea #

We need to:

• Look at every single character in the input string
• Verify each character is only '5' or '6'
• If any character fails this check, return False immediately. If all pass, return True.

Code Implementation #

def numberCheck(string):
    # Loop through each character in the input string
    for char in string:
        # Check if the character is NOT either '5' or '6'
        if char not in {'5', '6'}:
            return False
    # If we made it through the loop without returning False, all chars are valid
    return True

What's Happening Here? #

• The for char in string loop goes through each character one by one—this lets us validate every part of the input.
• The char not in {'5', '6'} check is the key: if the current character isn't in our set of allowed characters, we immediately return False (no need to check the rest, which saves a little time!).
• If the loop finishes without hitting a False, that means every character was either '5' or '6'—so we return True.

Handling Edge Cases (Optional) #

If you want to treat an empty string as invalid (since it has no 5s or 6s), just add a quick check at the start:

def numberCheck(string):
    # Return False if the string is empty
    if not string:
        return False
    for char in string:
        if char not in {'5', '6'}:
            return False
    return True

Test It Out! #

Try running these examples to make sure it works:

print(numberCheck("5566"))    # Output: True
print(numberCheck("56565"))   # Output: True
print(numberCheck("55a6"))    # Output: False (has an 'a')
print(numberCheck("7"))       # Output: False (has a '7')
print(numberCheck(""))        # Output: False (if you added the empty string check)

内容的提问来源于stack exchange，提问作者GSku0046