如何在 Python 中排除特定类型的输入变量？

Question

我创建了一行斐波那契数列。在开始时需要输入数字来指定斐波那契数列的大小，实际上是行的大小。数字必须是>=2的整数。

结果是打印出所有斐波那契数，直到行的最后一个数，以及它们各自的索引！之后需要取出一行的切片，结果是打印出切片内的所有数字及其各自的索引。

我成功地排除了所有不在指定范围内的值，但是我没有成功排除数字和其他不需要的类型的输入，例如想排除输入变量的浮点类型和字符串类型一个输入变量。

我指定不希望的输入变量类型是浮点数和字符串！但是它报告我一个错误！如何克服这个问题，或者换句话说，如何指定排除浮动变量和字符串变量的要求以不向我报告错误？

代码：

while True:
    n = int(input('Please enter the size of Fibonacci row - positive integer number(N>=2)!'))

    if n < 2:
        print('This is not valid number! Please enter valid number as specified above!')
        continue
    elif type(n)==float: # this line is not working!
        print('The number has to be an integer type, not float!')
        continue
    elif type(n)==str: # this line is not working!
        print(  'The number has to be an integer type, not string!')
        continue
    else:
        break

def __init__(self, first, last):
    self.first = first
    self.last = last

def __iter__(self):
    return self

def fibonacci_numbers(n):
    fibonacci_series =  [0,1]
    for i in range(2,n):
        next_element = fibonacci_series[i-1] + fibonacci_series[i-2]
        fibonacci_series.append(next_element)
    return fibonacci_series

while True:
    S = int(input('Enter starting number of your slice within Fibonacci row (N>=2):'))

    if S>n:
        print(f'Starting number can not be greater than {n}!')
        continue
    elif S<2:
        print('Starting number can not be less than 2!')
        continue
    elif type(S)==float: # this line is not working!
        print('The number can not be float type! It has to be an integer!')
        continue
    elif type(S)==str: # this line is not working!
        print('Starting number can not be string! It has to be positive integer number greater than or equal to 2!')
        continue
    else:
        break

while True:
    E = int(input(f'Enter ending number of your slice within Fibonacci row(E>=2) and (E>={S}):'))

    if E<S:
        print('Ending number can not be less than starting number!')
        continue
    elif E>n:
        print(f'Ending number can not be greater than {n}')
        continue
    elif E<2:
        print('Ending number can not be greater than 2!')
        continue
    elif type(E)==float: # this line is not working!
        print('Ending number can not be float type! It has to be an integer type!')
        continue
    elif type(E) ==str: # this line is not working!
        print(f'Ending number can not be string! It has to be positive integer number greater than or equal to {S}')
        continue
    else:
        break

print('Fibonacci numbers by index are following:')
for i, item in enumerate(fibonacci_numbers(n),start = 0):
    print(i, item)

fibonacci_numbers1 = list(fibonacci_numbers(n))
print('Fibonacci numbers that are within your slice with their respective indices are following:')
for i, item in enumerate(fibonacci_numbers1[S:E], start = S):
    print(i, item)

Answer 1

已解决 :-) 只需在您的代码中添加 try except 块，如下所示：

while True:
  try:
    num = int(input("Enter an integer number: "))
    break
  except ValueError:
      print("Invalid input. Please input integer only")  
      continue

print("num:", num)

投票和检查:-)

Answer 2

在第一行

    n = int(input('Please enter the size of Fibonacci row - positive integer number(N>=2)!'))

您正在将输入转换为 int，因此无论用户提供什么，它都会被转换为 int。

如果你想让你的代码正常工作，用这个替换它

n = input('Please enter the size of Fibonacci row - positive integer number(N>=2)!')

Answer 3

使用try/except/else 测试输入。如果字符串值不是严格的整数，int() 会引发 ValueError。

>>> while True:
...   s = input('Enter an integer: ')
...   try:
...     n = int(s)
...   except ValueError:
...     print('invalid')
...   else:
...     break
...
Enter an integer: 12a
invalid
Enter an integer: 1.
invalid
Enter an integer: 1.5
invalid
Enter an integer: 1+2j
invalid
Enter an integer: 5
>>>

Answer 4

如果您需要检查类型，isinstance 通常更好，例如。 g.：

if isinstance(var, int) or isinstance(var, str):
    pass  # do something here