Python module does not recognize module variable

Question

I have the following python module:

paths = {}

...

def execute_query(query_to_execute, *args, **kwargs):
    if 'paths' in kwargs:
        paths = kwargs['paths']

    queries = {
        'postgresqlVersion': '''{{postgresqlVersion}}''',
        'entityRelationships': '''{{entityRelationships (entity: "{}") {{name}}}}''',
        'path': '''{{path(name: "{}", path: "{}", annotate: "{}")}}''',
        'path_step': '''{{pathStep(name: "{}", step: "{}", key: {})}}'''
    }
    schema = graphene.Schema(query=Query)

    #schema.execute('''{path(name: "Ventas", path: "general_state/general_city/inventory_store/operations_sale", annotate: "_count")}''')

    result = schema.execute(queries[query_to_execute].format(*list(kwargs.values())))
    dict_result = dict(result.data.items())

    return {'top': dict_result, 'full': paths}

The problem is that the code only works if I remove the first two lines of method execute_query(). If I leave them, I get this error:

File "/Users/hugovillalobos/Documents/Code/agrowareproject/backend/query.py", line 236, in execute_query
    return {'top': dict_result, 'full': paths}
UnboundLocalError: local variable 'paths' referenced before assignment

I don't know why python does not recognize variable paths as the one declared in the first line of the module.

You make it local by assigning to it, even if that assignment is conditional. You need to do `global paths` to use global here. If you just want `paths` to be a default, a better option would be something like `l_paths = kwargs.get('paths', paths)`. — jordanm, Nov 02 '20 at 21:41
TL;DR - just for the fact that the line `paths = kwargs['paths']` is there, `paths` is considered a ***local*** variable to the function. In cases where `'paths' not in kwargs`, it is not defined. You should probably make it `global` or just pass it as an explicit argument... — Tomerikoo, Nov 02 '20 at 21:55

Amir Afianian · Answer 1 · 2020-11-02T22:01:49.020

A variable is global so long as you have not assigned it a value in your function. The latter makes the variable local. Even if, like in your case, the condition is not satisfied.

Note: The use of global variables is discouraged.

I suggest you modify your code as below:

def execute_query(query_to_execute, *args, **kwargs):

    paths = kwargs.get('paths', {})

    queries = {
        'postgresqlVersion': '''{{postgresqlVersion}}''',
        'entityRelationships': '''{{entityRelationships (entity: "{}") {{name}}}}''',
        'path': '''{{path(name: "{}", path: "{}", annotate: "{}")}}''',
        'path_step': '''{{pathStep(name: "{}", step: "{}", key: {})}}'''
    }
    schema = graphene.Schema(query=Query)

    #schema.execute('''{path(name: "Ventas", path: "general_state/general_city/inventory_store/operations_sale", annotate: "_count")}''')

    result = schema.execute(queries[query_to_execute].format(*list(kwargs.values())))
    dict_result = dict(result.data.items())

    return {'top': dict_result, 'full': paths}

If you insist on having the paths as a global variable, you can take the following approach (using the variable, but, not assigning to it)

paths = {}

....

def execute_query(query_to_execute, *args, **kwargs):

    new_paths = kwargs.get('paths', paths)

    queries = {
        'postgresqlVersion': '''{{postgresqlVersion}}''',
        'entityRelationships': '''{{entityRelationships (entity: "{}") {{name}}}}''',
        'path': '''{{path(name: "{}", path: "{}", annotate: "{}")}}''',
        'path_step': '''{{pathStep(name: "{}", step: "{}", key: {})}}'''
    }
    schema = graphene.Schema(query=Query)

    #schema.execute('''{path(name: "Ventas", path: "general_state/general_city/inventory_store/operations_sale", annotate: "_count")}''')

    result = schema.execute(queries[query_to_execute].format(*list(kwargs.values())))
    dict_result = dict(result.data.items())

    return {'top': dict_result, 'full': new_paths}

Python module does not recognize module variable

1 Answers1