Hope the following description sums it up well:
There are two things to consider here - variables and objects.
1.) If you are passing a variable, then it's pass by value, which means the changes made to the variable within the function are local to that function and hence won't be reflected globally. This is more of a 'C' like behavior.
- If you are passing a variable, then it's pass by value, which means the changes made to the variable within the function are local to that function and hence won't be reflected globally. This is more of a 'C' like behavior.
Example:
def changeval( myvar ):
myvar = 20;
print "values inside the function: ", myvar
return
myvar = 10;
changeval( myvar );
print "values outside the function: ", myvar
O/P:
values inside the function: 20
values outside the function: 10
2a.) If you are passing the variables packed inside a mutable object, like a list, then the changes made to the object are reflected globally as long as the object is not re-assigned.
values inside the function: 20
values outside the function: 10
- If you are passing the variables packed inside a mutable object, like a list, then the changes made to the object are reflected globally as long as the object is not re-assigned.
Example:
def changelist( mylist ):
mylist2=['a'];
mylist.append(mylist2);
print "values inside the function: ", mylist
return
mylist = [1,2,3];
changelist( mylist );
print "values outside the function: ", mylist
O/P:
values inside the function: [1, 2, 3, ['a']]
values outside the function: [1, 2, 3, ['a']]
2b.) Now consider the case where the object is re-assigned. In this case, the object refers to a new memory location which is local to the function in which this happens and hence not reflected globally.
values inside the function: [1, 2, 3, ['a']]
values outside the function: [1, 2, 3, ['a']]
- Now consider the case where the object is re-assigned. In this case, the object refers to a new memory location which is local to the function in which this happens and hence not reflected globally.
Example:
def changelist( mylist ):
mylist=['a'];
print "values inside the function: ", mylist
return
mylist = [1,2,3];
changelist( mylist );
print "values outside the function: ", mylist
O/P:
values inside the function: ['a']
values outside the function: [1, 2, 3]
values inside the function: ['a']
values outside the function: [1, 2, 3]
