CODEWITHSUNDEEP
pythonvariables
henry
henry

Reputation: 1

How do I change a global variables contents within a function

I have created the following sample program to demonstrate what I'm trying to do:

name = "d"

def namechange (name):

    global name
    name = "Henry"
    return name

print name

The errors that is produced:

SyntaxError: name 'name' is local and global

I understand that the name variable is local and global, but I am new to this and do not know how to resolve this issue. Please help

Upvotes: 0

Views: 161

Answers (2)

Chris
Chris

Reputation: 22953

Python considers function parameters as local variable. So since your function is accepting a parameter also named name, Python now considers name to be a local variable:

>>> global_variable = 0
>>> def foo(global_variable): # your creating a local variable here.
    global global_variable

SyntaxError: name 'global_variable' is parameter and global
>>>

The fix is to remove name from your functions parameters. That way, Python will see name as a global variable:

name = "d"   

def namechange (): # remove name
    global name
    name = "Henry"

print name

However, you should avoid using globals when you can. In this case, it would be a better solution to pass name as a parameter to your function, and let the caller deal with updating the variable:

name = "d"   

def namechange (name):
    name = "Henry"
    return name

new_name = namechange(name)
print new_name

Upvotes: 1

poke
poke

Reputation: 387507

def namechange (name):

This introduces a local variable name.

global name

Yet this also introduces the global variable name in the same scope.

Hence the syntax error that name is both local and global. In order to fix this, you have to either remove the local variable, or the global variable. In your case, you could do both.

You could either remove the local variable and just make the function modify the global variable, like this:

def namechange ():
    global name
    name = "Henry"

In that case, you don’t actually need to return anything, since this already modifies the global variable.

Or you could remove the global variable, and make this function just return the new value:

def namechange (name):
    name = "Henry"
    return name

In that case, it would be the caller’s responsibility to update the variable from the outer scope:

name = "d"
new_name = namechange(name)
print(new_name) # Henry

Upvotes: 1

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