如何让 Python 检查变量是数字还是字母？

Question

Hi I have a question...

As a Python beginner I want to ask how do I make my code to check is input from a user a number or a letter ?

if age == int or float:
    print("Ok, zavrsili smo sa osnovnim informacijama! Da li zelite da ih uklopimo i pokazemo Vase osnovne informacije? DA ili NE ?")

elif age == False:
    print("Hej, to nije broj... Pokusaj ponovo")

This is part of my code that I'm having issues with. I want to make statement if user inputs his age as number, the code continues . But, if user inputs something that is not a number, code tells him to start all over ( all print statements are written in Serbian, I hope you don't mind:D)

Answer 1

The easiest way to do this is to prompt the user for input in a while loop, try to convert it to a float , and break if you're successful.

while True:
    try:
        age = float(input("Please enter your age as a number: "))
        break
    except ValueError:
        print("That's not a number, please try again!")

# age is guaranteed to be a numeric value (float) -- proceed!

Answer 2

isinstance(x, int) # True

Or you can try

Use assert statement

assert <condition>,<error message>

for example

assert type(x) == int, "error"

Answer 3

Assuming that you are getting the value 'age' from the user via an input(..) call then to check if the age is a number then:

age = input('Provide age >')
if age.isnumeric():
    age = int(age)
    print("Ok, zavrsili smo sa osnovnim informacijama! Da li zelite da ih uklopimo i pokazemo Vase osnovne informacije? DA ili NE ?")
else:
     print("Hej, to nije broj... Pokusaj ponovo")

Answer 4

Using function to check type of string

def get_type(s):
    ''' Detects type of string s
    
       Return int if int, float if float, or None for non-numeric string '''
    if s.isnumeric():
        return int      # only digits
    elif s.replace('.', '', 1).isnumeric():
        return float    # single decimal
    else:
        return None     # returns None for non-numeric string


# Using function
age = input("What is your age?")
if not get_type(age) is None:
    print(f'Valid age {age}')
else:
    print(f'Value {age} is not a valid age')

Example runs

What is your age?25
Valid age 25

What is your age?12.5
Valid age 12.5

What is your age?12.3.5
Value 12.3.5 is not a valid age