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()

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