Python Scoping

See, Python has a fun interpretation of scoping. Let’s say I define a variable and a function at the same level, then access the variable from the function; the function will read the variable just fine. This is because Python looks for the variable in the current scope, then bumps up a scope level, looks again, etc. until it finds it or runs out of scope.

my_var = 'abcd'

def my_func():
    print my_var
    
my_func()
> "abcd"

However, things change when you write to the variable. At that point, if the variable doesn’t already exist in this scope, Python will create it, regardless of whether it’s in a different scope. Again, this is all logical, but it looks a little weird.

my_var = 'abcd'

def my_func():
    print my_var
    my_var = 'defg'
    print my_var

my_func()
> "abcd"
> "defg"

print my_var
> "abcd"