12) Trying to use a Python keyword for a variable name. (Causes “SyntaxError: invalid syntax”)

The Python keywords (also called reserved words) cannot be used for variable names. This happens with code like:

class = 'algebra'

The Python 3 keywords are: and, as, assert, break, class, continue, def, del, elif, else, except,False, finally, for, from, global, if, import, in, is, lambda, None, nonlocal, not, or, pass, raise,return, True, try, while, with, yield

13) Using an augmented assignment operator on a new variable. (Causes “NameError: name 'foobar' is not defined”)

Do not assume that variables start off with a value such as 0 or the blank string. A statement with an augmented operator like spam += 1 is equivalent to spam = spam + 1. This means that there must be a value in spam to begin with.

This error happens with code like this:

spam = 0

spam += 42

eggs += 42

14) Using a local variable (with the same name as a global variable) in a function before assigning the local variable. (Causes “UnboundLocalError: local variable 'foobar' referenced before assignment”)

Using a local variable in a function that has the same name as a global variable is tricky. The rule is: if a variable in a function is ever assigned something, it is always a local variable when used inside that function. Otherwise, it is the global variable inside that function.

This means you cannot use it as a global variable in the function before assigning it.

This error happens with code like this:

someVar = 42

def myFunction():

print(someVar)

someVar = 100

myFunction()