如何检查输入是否是Python中的数字？ [英] How do I check if input is a number in Python?

问题描述

我有一个Python脚本，它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，而不是任何其他会阻止脚本。

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

我尝试过if / else语句，但我真的不知道如何去做。我试过如果decimal.isint（）：和，如果decimal.isalpha（）：但他们只是抛出错误当我输入一个字符串。

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.")

如果没有if / else语句，代码就可以正常运行。

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

推荐答案

如果 int（）调用成功，十进制 已经一个数字。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:]

而不是使用 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，不带前导文本：

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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