You might have encountered some functions written in python which have a
return keyword in the end of the function. Do you know what it does? It
is similar to return in other languages. Lets examine this little
function:
def add(value1, value2):
return value1 + value2
result = add(3, 5)
print(result)
# Output: 8The function above takes two values as input and then output their addition. We could have also done:
def add(value1,value2):
global result
result = value1 + value2
add(3,5)
print(result)
# Output: 8So first lets talk about the first bit of code which involves the
return keyword. What that function is doing is that it is assigning
the value to the variable which is calling that function which in our
case is result. In most cases and you won't need to use the
global keyword. However lets examine the other bit of code as well
which includes the global keyword. So what that function is doing is
that it is making a global variable result. What does global mean
here? Global variable means that we can access that variable outside the
scope of the function as well. Let me demonstrate it with an example :
# first without the global variable
def add(value1, value2):
result = value1 + value2
add(2, 4)
print(result)
# Oh crap we encountered an exception. Why is it so ?
# the python interpreter is telling us that we do not
# have any variable with the name of result. It is so
# because the result variable is only accessible inside
# the function in which it is created if it is not global.
Traceback (most recent call last):
File "", line 1, in
result
NameError: name 'result' is not defined
# Now lets run the same code but after making the result
# variable global
def add(value1, value2):
global result
result = value1 + value2
add(2, 4)
result
6So hopefully there are no errors in the second run as expected. In
practical programming you should try to stay away from global
keyword as it only makes life difficult by introducing unwanted variables
to the global scope.