如何检查输入是否是 Python 中的数字?

2022-01-17 00:00:00 python input numbers if-statement

问题描述

我有一个 Python 脚本，可以将十进制数转换为二进制数，这显然使用了他们的输入.

I have a Python script which converts a decimal number into a binary one and this obviously uses their input.

我想让脚本验证输入是一个数字，而不是其他任何会停止脚本的东西.

I would like to have the script validate that the input is a number and not anything else which will stop the script.

我尝试了 if/else 语句，但我真的不知道该怎么做.我试过 if decimal.isint(): 和 if decimal.isalpha(): 但当我输入字符串时它们只会抛出错误.

I have tried an if/else statement but I don't really know how to go about it. I have tried if decimal.isint(): and if decimal.isalpha(): but they just throw up errors when I enter a string.

print("Welcome to the Decimal to Binary converter!")
while True:
    print("Type a decimal number you wish to convert:")
    decimal = int(input())
    if decimal.isint():
        binary = bin(decimal)[2:]
        print(binary)
    else:
        print("Please enter a number.")

没有 if/else 语句，代码可以正常工作并完成其工作.

Without the if/else statement, the code works just fine and does its job.

解决方案

如果int()调用成功，decimal是已经数字.您只能在字符串上调用 .isdigit() (正确的名称):

If the int() call succeeded, decimal is already a number. You can only call .isdigit() (the correct name) on a string:

decimal = input()
if decimal.isdigit():
    decimal = int(decimal)

另一种方法是使用异常处理；如果抛出 ValueError，则输入不是数字:

The alternative is to use exception handling; if a ValueError is thrown, the input was not a number:

while True:
    print("Type a decimal number you wish to convert:")
    try:
        decimal = int(input())
    except ValueError:
        print("Please enter a number.")
        continue

    binary = bin(decimal)[2:]

除了使用 bin() 函数并删除起始 0b，您还可以使用 format()函数，使用'b'格式，将整数格式化为二进制字符串, 没有前导文本:

Instead of using the bin() function and removing the starting 0b, you could also use the format() function, using the 'b' format, to format an integer as a binary string, without the leading text:

>>> format(10, 'b')
'1010'

format() 函数可以轻松添加前导零:

The format() function makes it easy to add leading zeros:

>>> format(10, '08b')
'00001010'

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