如何在通过 int() 之前检查字符串是否为负数? [英] How do I check if a string is a negative number before passing it through int()?

问题描述

我正在尝试编写一些东西来检查字符串是数字还是负数.如果它是一个数字(正数或负数)，它将通过 int() 传递.不幸的是，当包含-"时，isdigit() 不会将其识别为数字.

I'm trying to write something that checks if a string is a number or a negative. If it's a number (positive or negative) it will passed through int(). Unfortunately isdigit() won't recognize it as a number when "-" is included.

这是我目前所拥有的:

def contestTest():
# Neutral point for struggle/tug of war/contest
x = 0

while -5 < x < 5:
    print "Type desired amount of damage."
    print x
    choice = raw_input("> ")

    if choice.isdigit():
        y = int(choice)
        x += y
    else:
        print "Invalid input."

if -5 >= x:
    print "x is low. Loss."
    print x
elif 5 <= x:
    print "x is high. Win."
    print x
else:
    print "Something went wrong."
    print x

我能想到的唯一解决方案是一些单独的、令人费解的语句系列，我可能会将它们放在一个单独的函数中以使其看起来更好.如有任何帮助，我将不胜感激！

The only solution I can think of is some separate, convoluted series of statements that I might squirrel away in a separate function to make it look nicer. I'd be grateful for any help!

推荐答案

您可以轻松地先删除左边的字符，如下所示:

You can easily remove the characters from the left first, like so:

choice.lstrip('-+').isdigit()

然而，处理来自无效输入的异常可能会更好:

However it would probably be better to handle exceptions from invalid input instead:

print x
while True:
    choice = raw_input("> ")
    try:
        y = int(choice)
        break
    except ValueError:
        print "Invalid input."
x += y

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