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mauricio
Asked: 2020-03-31 16:25:51 +0800 CST 2020-03-31 16:25:51 +0800 CST

How to show how many characters a variable has where numbers entered by keyboard are stored?

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I want that when the user types a phone number by keyboard it is saved in this variable (number)

number = input(int("digite un numero teléfono :"))

and then return if those numbers that are stored in the variable have more than 9 characters. I did it this way but I couldn't.

if number.len > 9:
  print("introduciste mas de 9 numeros")
python-3.x

1 Answers

  1. Best Answer

    First, inside the input you only have to place the message that you want to be shown to the user, what you want to do would be done in this way

    number = int(input("Enter a phone number :"))

    But that would cause an error if the user enters letters, for now I'll tell you my proposed solution which doesn't include that method.

    number = input("Digite un numero teléfono :")

while not number.isdigit() or len(number) > 9:
    number = input("Digite un numero de teléfono válido:")

print(number)

    The user is prompted to enter the phone number.

    First, isdigit() evaluates a string and if it is clearly numbers, it returns a boolean value True, otherwise it returns False, if for example we evaluate the following:

    foo = "Hola123"
print(foo.isdigit())

    That will return Falsebecause the variable foodoes not contain only numbers, and since there is a combination of numbers and letters, it becomes a string.

    Ok, so in the loop while, when we prefix notthe evaluation of the variable numberin simple words we are saying:

    While the evaluation of number.isdigit()NOT returns Truewill execute what is inside the while, remember that a loop whilewill execute until one of its conditions (or the only one it has) is false, that is False. So when we enter a stringin our script, it number.isdigit()returns False, and as we said before, as long as number.isdigit()no ( not) returns we Truewill execute the contents of the loop while. Now, the second condition is easier, if the length of the entered value is greater than 9, we will continue to execute the while.

    So, as we say, as long as the loop whilekeeps getting True values, it will keep executing, let's put it like this:

    If the variable numberis equal to:

    • "Hello" = A valid number will continue to be requested, because they are not numbers
    • "123" = The script will end, because there are no letters and the length is less than 9.
    • "1234567890" = A valid number will continue to be requested, because it exceeds the set limit.

    With this cycle while, 2 birds are killed with one stone, it is evaluated if what is entered is a number and its length, you only have to understand how a while cycle works to understand what is happening.

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