48 – Redacting email addresses

You can use f-strings and the string formatting specification language to create an effect of redacted or private data. For example, the function below redacts part of your email address:

def redact_email(email):
    user, _, domain = email.partition("@")
    return f"{user[:2]:*<{len(user)}}@{domain}"

print(redact_email("rodrigo@mathspp.com"))
# ro*****@mathspp.com

The part that is doing the heavy lifting is the section *<{len(user)} inside the f-string formatting:

1. {len(user)} uses the length of the variable user to determine the width of the field where user[:2] (the first two characters of the user) will be inserted;

2. < tells Python to align user[:2] on the left of that field; and

3. * tells Python to fill empty space with the character asterisk.

You could modify the function to also mask the domain, for example.

Note: for very security-sensitive use-cases, you might want to randomise the number of asterisks shown, instead of making the string match the correct length.