python - 我正在尝试添加一个 if 语句来检查输入是否是带有 python3 的字符串，无论如何在传递参数时返回错误

Question

我是一名学习如何编码的初学者。我编写了以下代码，因为我正在尝试学习如何处理输入是字符串而不是数字的问题。

目前正在运行Python3.7.3，我尝试使用.isalpha()。我首先尝试了 if numOfGuests.isalpha: 和 numOfGuests == str(numOfGuests) 但它们也不起作用。 intellisense 告诉我第 8 行有语法错误，if 有下划线。为什么？我还在学习，所以我不确定我做错了什么

name = ''

while not name:
    print('Enter your name ')
    name = input()
print ('How many guests will you have')
numOfGuests = input()
if numOfGuests == str(numOfGuests)
    print('those are letters, not numbers')
    else:
      pass
if numOfGuests == int()
    print('Be sure that you have enough room for all your guests')
print('Done')

我希望系统只打印“这些是字母，而不是数字”，然后从“你有多少客人”开始

错误信息:

SyntaxError: invalid syntax
PS C:\Users\name\Desktop\python> cd 'c:\Users\name\Desktop\python'; ${env:PYTHONIOENCODING}='UTF-8'; ${env:PYTHONUNBUFFERED}='1'; & 'C:\Python\Python37\python.exe' 'c:\Users\name\.vscode\extensions\ms-python.python-2019.6.22090\pythonFiles\ptvsd_launcher.py' '--default' '--client' '--host' 'localhost' '--port' 'omitted for security' 'c:\Users\name\Desktop\python\truthy and falsey.py' Traceback (most recent call last):
  File "c:\Users\name\.vscode\extensions\ms-python.python-2019.6.22090\pythonFiles\ptvsd_launcher.py", line 43, in <module>
    main(ptvsdArgs)
  File "c:\Users\name\.vscode\extensions\ms-python.python-2019.6.22090\pythonFiles\lib\python\ptvsd\__main__.py", line 434, in main
    run()
  File "c:\Users\name\.vscode\extensions\ms-python.python-2019.6.22090\pythonFiles\lib\python\ptvsd\__main__.py", line 312, in run_file
    runpy.run_path(target, run_name='__main__')
  File "C:\Python\Python37\lib\runpy.py", line 261, in run_path
    code, fname = _get_code_from_file(run_name, path_name)
  File "C:\Python\Python37\lib\runpy.py", line 236, in _get_code_from_file
    code = compile(f.read(), fname, 'exec')
  File "c:\Users\name\Desktop\python\truthy and falsey.py", line 8
    if numOfGuests == str(numOfGuests)
                                     ^
SyntaxError: invalid syntax

Answer 1

除了评论中提出的其他问题之外，您还假设使用 str() 和 int() 等类型进行测试会告诉您字符串变量。那不是一个有效的想法。这是我能想到的最直接的代码版本，它可以满足我的要求:

name = ''

while not name:
    print('Enter your name ')
    name = input()
print ('How many guests will you have')
numOfGuests = input()
if not numOfGuests.isdecimal():
    print('those are letters, not numbers')
else:
    print('Be sure that you have enough room for all your guests')
print('Done')

这里还有很多可以改进的地方，但我认为让你着手实际运行的东西将有助于你继续学习。例如，有更好的方法来检查有效的数字输入。