Unable to import another python module same level

Question

I have a file called

server.py

another called constants.py

constants.py

is on the same level as server.py

Here is what I am doing:

server.py

import constants
def hello_world():
   print(BUCKET_NAME)

constants.py

BUCKET_NAME = 'uw-note-share'

I am getting the error:

NameError: global name 'BUCKET_NAME' is not defined

Even though I am properly importing. What is the issue?

Answer 1

Take a look at the documentation:

Enter the Python interpreter and import this module with the following command: import fibo This does not enter the names of the functions defined in fibo directly in the current symbol table; it only enters the module name fibo there.

Each module has its own private symbol table, which is used as the global symbol table by all functions defined in the module. Thus, the author of a module can use global variables in the module without worrying about accidental clashes with a user’s global variables. On the other hand, if you know what you are doing you can touch a module’s global variables with the same notation used to refer to its functions, modname.itemname.

This may seem very complicated, but what it says is basically, when you import a module, all of its contents remain in a separate namespace in order to prevent collisions (i.e. two variables in two modules with the exact same name).

Lets take your example. For your code to work you have two options.

Option A

Explicitly tell python that the variable you're looking for is defined in the constants module.

import constants
def hello_world():
   print(constants.BUCKET_NAME)

Option B

Again, from the documentation:

There is a variant of the import statement that imports names from a module directly into the importing module’s symbol table.

This variant is the following:

from module import x

What this does is it imports everything one by one from the constants module. From then on, python treats that data as if it was defined in your current module.

Using this approach, you can do the following:

from constants import *
def hello_world():
   print(BUCKET_NAME)

The * here tells python to import everything from that module. This is convenient in a lot of cases, however be advised, this may cause performance issues when dealing with large modules. Also, keep in mind:

This does not introduce the module name from which the imports are taken in the local symbol table

What this means is that if you opt to only import BUCKET_NAME from constants (from constants import BUCKET_NAME instead of import *), constants won't be defined. You will not be able to access other variables defined in that module without also writing import constants.

For a more detailed explanation regarding the performance of the latter approach, take a look at this excellent post by Roberto Liffredo, as well as this by resident python master Martijn Pieters.

Answer 2

Try ,

from constants import BUCKET_NAME
print(BUCKET_NAME)

Or you could,

import constants
print(constants.BUCKET_NAME)

When we import a module, we are making it available to us in our current program as a separate namespace. This means that we will have to refer to the function in dot notation, as in [module].[function].

Answer 3

You are trying to import whole file itself. You can get it to work in two ways,

import constants
def hello_world():
   print(constants.BUCKET_NAME)

OR

from constants import BUCKET_NAME
def hello_world():
   print(BUCKET_NAME)

I hope this helps you.