Python Validation Errors

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You know the ones I’m talking about those ***** little messages that pop up when you try to run your code and it just doesn’t work. No worries, though, bro, for today we will learn how to handle these errors like pros!

First things first, what validation errors are. In simple terms, they occur when the input provided by a user does not meet certain criteria or expectations set forth in your code. For example, if you have a function that takes an integer as its argument and someone tries to pass it a string instead, you will get a validation error.

Now, Let’s get cracking with some examples of common validation errors and how we can handle them using Python.

Example 1: Invalid Input Type
Let’s say you have a function that calculates the square root of a number. If someone tries to pass it a string instead of an integer or float, you will get a type error. To avoid this, you can add some input validation at the beginning of your function using an if statement:

# Function to calculate the square root of a number
def calculate_square_root(num):
    # Check if the input is an integer or a floating-point number
    if not isinstance(num, (int, float)):
        # If not, print an error message and return None
        print("Invalid Input Type! Please provide either an integer or a floating-point number.")
        return None
    
    # If the input is valid, calculate the square root
    square_root = num ** 0.5
    
    # Return the calculated square root
    return square_root

In this example, we’re using Python’s `isinstance()` function to check if the input is either an int or float. If it isn’t, we print out an error message and return None (which will prevent any further execution of our code).

Example 2: Invalid Input Range
Let’s say you have a function that calculates the factorial of a number. However, if someone tries to pass it a number greater than 10 or less than 0, you will get an error message. To avoid this, you can add some input validation at the beginning of your function using another if statement:

# This function calculates the factorial of a given number
def calculate_factorial(num):
    # Check if the input number is within the valid range of 0 to 10
    if num < 0 or num > 10:
        # If not, print an error message and return None
        print("Invalid Input Range! Please provide a number between 0 and 10.")
        return None
    
    # If the input number is within the valid range, proceed with calculating the factorial
    factorial = 1
    # Loop through all numbers from 1 to the input number
    for i in range(1, num+1):
        # Multiply the current factorial value by the current number
        factorial *= i
    
    # Return the calculated factorial
    return factorial

In this example, we’re using Python’s `or` operator to check if the input is less than zero or greater than ten. If it is, we print out an error message and return None (which will prevent any further execution of our code).

Example 3: Invalid Input Format
Let’s say you have a function that takes in a date as its argument. However, if someone tries to pass it a date in the wrong format (e.g., “1/2/2021” instead of “2021-01-02”), you will get an error message. To avoid this, you can add some input validation at the beginning of your function using another if statement:

# Define a function that takes in a date as its argument
def calculate_age(birthdate):
    # Import the datetime module as dt
    import datetime as dt
    
    # Use a try-except block to handle potential errors
    try:
        # Use the strptime() method to convert the birthdate string into a datetime object
        birth = dt.datetime.strptime(birthdate, '%Y-%m-%d')
        
    # If the input format is incorrect, catch the ValueError and print an error message
    except ValueError:
        print("Invalid Input Format! Please provide a date in the format YYYY-MM-DD.")
        # Return None to indicate that the function did not successfully calculate the age
        return None
    
    # Calculate age here...
    # (Code for calculating age is not shown as it is not relevant to the corrections)
    

calculate_age('1990-05-15')

# Output: None

# Call the function with an invalid date in the wrong format
calculate_age('1/2/2021')

# Output: Invalid Input Format! Please provide a date in the format YYYY-MM-DD.
# None

In this example, we’re using Python’s `datetime.strptime()` function to convert the input into a datetime object. If there is an error (e.g., wrong format), it will raise a ValueError exception which we catch and handle with our if statement. We print out an error message and return None (which will prevent any further execution of our code).

And that’s all for today, I hope this tutorial helped you understand how to handle validation errors in Python like a pro. Remember, always be kind to your users and provide clear error messages when things go wrong.

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