Python Forum
UnboundLocalError: local variable referenced before assignment
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
UnboundLocalError: local variable referenced before assignment
#1
Hi

Need some help here
Original code
def test1():
    test_list = []
    test_var = 0
    test_string1 = ""

    def test2():
        temp =2
        if temp > test_var:
            test_var = temp
        else:
            test_string = "fail"
        return test_string
    
    res = test2()
    print res

test1()
https://docs.python.org/3/faq/programming.html#why-am-i-getting-an-unboundlocalerror-when-the-variable-has-a-value

I used both global , nonlocal but both throws different error

def test1():
    test_list = []
    test_var = 0
    test_string1 = ""

    def test2():
        nonlocal test_var
        temp =2
        if temp > test_var:
            test_var = temp
        else:
            test_string = "fail"
        return test_string
    
    res = test2()
    print res

test1()
throws this error
nonlocal test_var ^
SyntaxError: invalid syntax


def test1():
    test_list = []
    test_var = 0
    test_string1 = ""

    def test2():
        global test_var
        temp =2
        if temp > test_var:
            test_var = temp
        else:
            test_string = "fail"
        return test_string
    
    res = test2()
    print res

test1()
throws this error ^
NameError: global name 'test_var' is not defined

Any suggestions ? I have gone through top 10 search results , all suggest to use nonlocal or global...
Reply
#2
This is topic with lot of subtlety. Some of the scenarios are discussed in this thread: Namespace and scope difference

I think that this boils down to this:

Quote:You should also understand difference between reference and assignment:

When you reference a variable in an expression, the Python interpreter will traverse the scope to resolve the reference in following order:

- current function’s scope
- any enclosing scopes (like containing functions)
- scope of the module that contains the code (global scope)
- built-in scope (that contains functions like int and abs)

If Python doesn't find defined variable with the referenced name, then a NameError exception is raised.

Assigning a value to a variable works differently. If the variable is already defined in the current scope, then it will just take on the new value. If the variable doesn’t exist in the current scope, then Python treats the assignment as a variable definition. The scope of the newly defined variable is the function that contains the assignment.
I'm not 'in'-sane. Indeed, I am so far 'out' of sane that you appear a tiny blip on the distant coast of sanity. Bucky Katt, Get Fuzzy

Da Bishop: There's a dead bishop on the landing. I don't know who keeps bringing them in here. ....but society is to blame.
Reply


Possibly Related Threads…
Thread Author Replies Views Last Post
  It's saying my global variable is a local variable Radical 5 1,097 Oct-02-2023, 12:57 AM
Last Post: deanhystad
  local varible referenced before assignment SC4R 6 1,465 Jan-10-2023, 10:58 PM
Last Post: snippsat
  How does UnboundLocalError work? deanhystad 3 1,633 Feb-25-2022, 01:21 AM
Last Post: bowlofred
  UnboundLocalError: local variable 'wmi' referenced before assignment ilknurg 2 1,855 Feb-10-2022, 07:36 PM
Last Post: deanhystad
  Referenced before assignment finndude 3 3,223 Mar-02-2021, 08:11 PM
Last Post: finndude
  exec + subprocess = UnboundLocalError paul18fr 6 3,441 Feb-04-2021, 06:27 AM
Last Post: Gribouillis
  ReferenceError: weakly-referenced object no longer exists MrBitPythoner 17 11,260 Dec-14-2020, 07:34 PM
Last Post: buran
  Assignment of non-existing class variable is accepted - Why? DrZ 6 4,186 Jul-13-2020, 03:53 PM
Last Post: deanhystad
  UnboundLocalError: local variable 'figure_perso' referenced before assignment mederic39 2 2,227 Jun-11-2020, 12:45 PM
Last Post: Yoriz
  UnBoundLocalError Seaninho 3 2,620 May-31-2020, 07:22 AM
Last Post: azajali43

Forum Jump:

User Panel Messages

Announcements
Announcement #1 8/1/2020
Announcement #2 8/2/2020
Announcement #3 8/6/2020