Python Validator Patterns

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But don’t worry, I won’t bore you with dry technical jargon or complicated examples. Instead, let’s have some fun and learn how to validate our data in Python like a boss (or at least try).

First things first, why do we need validation patterns? Well, because sometimes the input we receive from users is not what we expect it to be. Maybe they forgot to fill out a required field or entered an invalid email address. In these cases, our program needs to handle the situation gracefully and provide feedback to the user.

So Let’s get right into it with some of my favorite validation patterns in Python:

1) The “Is this a valid number?” pattern

This is probably one of the most common validation patterns out there. We want to make sure that our input can be converted to a float or an integer without any issues. Here’s how we do it:

# This function is used to validate if the input can be converted to a float or integer without any issues.
def validate_number(input):
    try:
        # The float() function converts the input to a floating-point number.
        num = float(input)
        # If the input can be converted successfully, the function returns True and the converted number.
        return True, num
    # If the input cannot be converted to a float, a ValueError will be raised.
    except ValueError:
        # Print an error message to inform the user that the input is not a valid number.
        print("Invalid number! Please enter a valid number.")
        # If the input cannot be converted, the function returns False and None.
        return False, None

In this example, we’re using a `try-except` block to catch any potential errors. If the input can be converted to a float without issues, we return True and the converted value. Otherwise, we print an error message and return False and None.

2) The “Is this a valid email address?” pattern

This one is a bit trickier than the previous one because there are many different ways to format an email address. However, we can use regular expressions (regex for short) to validate our input:

# Import the regular expression module
import re

# Define a function to validate an email address
def validate_email(input):
    # Define a regular expression pattern for a valid email address
    regex = r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
    # Use the match function to check if the input matches the pattern
    if re.match(regex, input):
        # If the input matches the pattern, return True
        return True
    else:
        # If the input does not match the pattern, print an error message
        print("Invalid email address! Please enter a valid email.")
        # Return False to indicate that the input is not a valid email address
        return False

In this example, we’re using the `re.match()` function to check if our input matches the regex pattern. If it does, we return True. Otherwise, we print an error message and return False.

3) The “Is this a valid URL?” pattern

This one is similar to the email validation pattern because we’re using regular expressions again:

# Import the regular expression module
import re

# Define a function to validate a URL
def validate_url(input):
    # Define the regex pattern for a valid URL
    regex = r'^https?://[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$'
    # Use the re.match() function to check if the input matches the regex pattern
    if re.match(regex, input):
        # If it does, return True
        return True
    else:
        # If it doesn't, print an error message and return False
        print("Invalid URL! Please enter a valid URL.")
        return False

In this example, we’re using the same regex pattern as before but with some modifications to match HTTP and HTTPS protocols. If it matches, we return True. Otherwise, we print an error message and return False.

4) The “Is this a valid password?” pattern

This one is a bit more complex because there are many different requirements for passwords (length, complexity, etc.). However, let’s keep things simple:

# This function checks if a given password meets certain requirements and returns True if it does, False if it doesn't.

def validate_password(input):
    # Check if the length of the input is less than 8 characters
    if len(input) < 8:
        # Print an error message and return False if it is
        print("Password must be at least 8 characters long.")
        return False
    # Check if the input contains at least one digit
    elif not any(char.isdigit() for char in input):
        # Print an error message and return False if it doesn't
        print("Password should contain a number.")
        return False
    # Check if the input contains at least one uppercase or lowercase letter
    elif not any(char.isupper() for char in input) and not any(char.islower() for char in input):
        # Print an error message and return False if it doesn't
        print("Password should contain at least one uppercase or lowercase letter.")
        return False
    # If all the above conditions are not met, the password is considered valid
    else:
        return True

In this example, we’re checking the length of our password first. If it’s less than 8 characters long, we print an error message and return False. Then we check if there is at least one digit in the password. Finally, we check if there is at least one uppercase or lowercase letter in the password.

And that’s it! These are just a few examples of validation patterns you can use to validate your data in Python. Remember, always handle errors gracefully and provide feedback to the user when something goes wrong.

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