Why Does `__import__` Fail to Fully Import Submodules in Python, and How Can I Fix It?

Understanding the import Function for Submodule Loading

In Python, importing modules plays a crucial role in organizing and reusing code. However, when attempting to import a submodule from a string variable using the import function, puzzling results may arise.

Problem:

Consider the following code:

import matplotlib.text as text
x = dir(text)

i = __import__('matplotlib.text')
y = dir(i)

j = __import__('matplotlib')
z = dir(j)

Comparing the three lists x, y, and z reveals unexpected differences. Specifically, list y lacks information about the main classes from the matplotlib.text submodule, which is present in list x.

Solution:

The import function requires careful understanding. By adding an empty string argument to the fromlist parameter, we can specify that we want to import the submodule itself:

i = __import__('matplotlib.text', fromlist=[''])

Now, variable i will reference the matplotlib.text submodule, and list y will contain the desired information.

Alternatively, starting from Python 3.1, we can use the importlib package:

import importlib

i = importlib.import_module("matplotlib.text")

Additional Notes:

• When importing files from sub-folders, use the following syntax: importlib.import_module("feature.email")
• In Python versions prior to 3.3, importing from sub-folders without an __init__.py file was not possible.

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