How Can I Reliably Verify if a String Represents a Number in Python?

Verifying Numeric Input in Strings

Determining whether a string represents a numerical value (e.g., 1, 0, -5) is a common coding challenge.

Naive Approach (Type Checking)

Intuitively, one may try to use the type checking operator (e.g., type(user_input) == int) to verify numericity. However, this approach falls short because the input function always returns a string.

Reliable Approach (Exception Handling)

A more robust method involves using exception handling to test for numeric conversions. Here's a Python example:

try:
    number = int(user_input)
except ValueError:
    print("That's not a valid number!")

This code block attempts to convert the user input (stored in user_input) to an integer (int). If the conversion succeeds, the variable number will hold the numerical value. However, if the input is non-numeric (e.g., "abc"), a ValueError exception is raised and the error message is printed.

The try-except block effectively filters out non-numeric inputs and allows the program to proceed with valid numerical data.

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