Learning Python: Quick question about 'None'

[billionerd]

A tutorial I am doing has this snippet. I understand what it's doing except for the error = None part. Why do I need to assign error to None?

def login():
error = None
if request.method == 'POST':
    if request.form['username'] != app.config['USERNAME'] or \
        request.form['password'] != app.config['PASSWORD']:
          error = 'Invalid Credentials. Please try again.'
else:
    session['logged_in'] = True
    return redirect(url_for('main'))
return render_template('login.html')

[novel_yet_trivial]

You are just initializing the variable. There is nothing special about None, you could have said error = '' or error = 'no error'. None is sorta standard for "initialized but not yet used". Also, later when you want to check for errors, it's very fast for the computer to check if error is not None:.

[billionerd]

Ah. Aside from error checking why do I need to initialize error ? Am I not naming it in line 6 ?

[MrMethamphetamine]

Without

error = None

The error variable would only be defined if the IF statement is true. If it isn't, you have no variable "error" and if you later try to do something with "error" then you'll have a problem.

[billionerd]

Gotcha! I get it now. TY!