# Main
email = input("Enter email: ")
check_valid_email(email)

def check_valid_email(email):
    valid = False
    for i in range(len(email)):
        if email[i:i+1] == "@":
            valid = True

    if valid == True:
        print("Valid email")
    else:
        print("Invalid email")

# Main
email = input("Enter email: ")
check_valid_email(email)

"""
Procedure: check_valid_email(email)
-----------------------------------
This procedure takes an email string as a parameter.

It checks the string one character at a time using a loop.
The line:
    if email[i:i+1] == "@":
means:
- Look at the substring starting at position i and ending at i+1.
- This gives exactly one character from the string.
- Compare that single character to "@".
If "@" is found anywhere in the string, we mark the email as valid.
Finally, the procedure prints either "Valid email" or "Invalid email".
"""
def check_valid_email(email):
    valid = False   # assume it is not valid to start with
    
    # loop through each position in the string
    for i in range(len(email)):
        # Take one character at position i
        # Compare it to "@"
        if email[i:i+1] == "@":
            valid = True
    
    # After the loop, check the result
    if valid == True:
        print("Valid email")
    else:
        print("Invalid email")


"""
Main program
------------
1. Ask the user to enter an email address.
2. Call the procedure check_valid_email(email)
   and pass the user input as the parameter.
"""
# Main
email = input("Enter email: ")
check_valid_email(email)