Python voltage input

Question

`Hi, I want to write a code to get inputs for both integer and float numbers but only numbers. If float number is given it accepts dot but not any other nonalphanumeric characters.

I wrote this code but it gives "Please enter the Frequency value:" error for float numbers, too.`

def signal_selection(signal_type):
   if signal_type == "1":  # Sine wave
        # Frekans değerini input olarak alır
        frequency = input("Please enter the Frequency value:")  # Hz
        while (frequency.isnumeric() != True):
            if frequency.isalpha():
                frequency = input("Please enter a valid number:")
            elif frequency.isnumeric() != True:
                frequency = input("Please enter a valid number:")
            elif frequency.isdigit() != True:
                frequency = input("Please enter a valid number:")
        frequency = float(frequency)
        print("Frequency:", frequency, "\n")

`isnumeric` only returns True for integers; see this post: https://stackoverflow.com/questions/354038/how-do-i-check-if-a-string-represents-a-number-float-or-int — Swifty, Jul 20 '23 at 15:14
@Swifty Not exactly. `'²'.isnumeric()` gives back `True`, but `int('²')` does not work. — Matthias, Jul 20 '23 at 15:59
Indeed, I realized I was very approximative; I should have said it doesn't acknowledge decimals. — Swifty, Jul 21 '23 at 07:23

score 1 · Answer 1 · answered Jul 20 '23 at 15:15

An easier way of doing it is by using the try-except construct:

def signal_selection(signal_type):
   if signal_type == "1":  # Sine wave
        # Frekans değerini input olarak alır
        frequency = input("Please enter the Frequency value:")  # Hz
        while True:
            try:
                frequency = float(frequency)
                break
            except ValueError:
                frequency = input("Please enter a valid number:")
        print("Frequency:", frequency, "\n")

i.e. trying to convert it to float and ask again if the conversion fails.

Mridul · Accepted Answer · 2023-07-20T17:20:37.230

As mentioned by @Swifty, the isnumeric check doesnt work for float-like strings. Therefore, frequency.isnumeric() != True becomes true on entering a float-like string and causes another input to take place.

An easier and alternate way of doing this is using error handling along with a while loop:

def signal_selection(signal_type):
    if signal_type == "1":  # Sine wave
        # Frekans değerini input olarak alır
        frequency = input("Please enter the Frequency value:")  # Hz
        valid_input = False
        while not valid_input:
            try:
                frequency = float(frequency)
            except ValueError:
                frequency = input("Please enter a valid number:")
            else:
                valid_input = True
        print("Frequency:", frequency, "\n")

score -1 · Answer 3 · answered Jul 20 '23 at 15:15

-1

What about using the following function to check the number:

def is_number(n):
    try:
        float(n)
    except ValueError:
        return False
    return True

answered Jul 20 '23 at 15:15

Alireza Roshanzamir

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Python voltage input

3 Answers3