I have a habit to do leetcode questions sequentially. Last week I encountered 14 questions in a row about Pandas, which I think worth to do a little recap to enhance my memory. When I was learning Machine Learning 7-8 years ago. (The famous course on Coursera by Andrew Ng.) I was using Octave and then didn’t touch Python / Pandas for a long time as I am a full-stack .NET guy. Before I can start solving those questions. I have to setup the testing environment to verify my code. It is always good to document how do I setup such a Python unit-testing environment from scratch. This is more easier to use than I was expected, except some discrepancy during Python setup.

Setup Python

1. Check if Python installed:

python3 --version

If not:

brew install python3

2. Create virtual environment, isolated environment with a standalone python installation with pip installed in root directory:

python3 -m venv .

3. Activate the virtual environment:

source bin/activate

4. Install pytest:

python3 -m pip install pytest

5. Deactivate the virtual environment (In case needed)

deactivate

Setup Python unit-testing

There are two major unit testing framework in Python:

• unittest
• pytest

pytest vs unittest

Feature	pytest	unittest
Installation	Third-party (pip install pytest)	Built-in (part of standard library)
Test Structure	Function-based	Class-based
Boilerplate Code	Less	More
Assertions	Simple assert statements	Methods like self.assertEqual
Advanced Features	Fixtures, parameterized testing, plugins	Limited
Test Discovery	Automatic	Requires unittest discovery

I choose pytest as it work in a modern way.

To use pytest:

pip install pytest

To run test for a file

pytest filename.py

To get output from print()

pytest -s filename.py

Run all tests in a folder

pytest

Test files must either start with test_ or end with _test.py

And you are all done:

% pytest
===== test session starts =====
platform darwin -- Python 3.13.1, pytest-8.3.4, pluggy-1.5.0
rootdir: /Users/ferrywlto/Documents/GitHub/Personal/kata-dojo/python/leetcode
collected 15 items                                                                                        

easy/q2877_create_dataframe_from_list_test.py  [  6%]
easy/q2878_get_size_of_dataframe_test.py       [ 13%]
easy/q2879_display_first_three_rows_test.py    [ 20%]
easy/q2880_select_data_test.py                 [ 26%]
easy/q2881_create_new_column_test.py           [ 33%]
easy/q2882_drop_duplicate_rows_test.py         [ 40%]
easy/q2883_drop_missing_data_test.py           [ 46%]
easy/q2884_modify_columns_test.py              [ 53%]
easy/q2885_rename_column_test.py               [ 60%]
easy/q2886_change_data_type_test.py            [ 66%]
easy/q2887_fill_missing_data_test.py           [ 73%]
easy/q2888_reshape_data_concatenate_test.py    [ 80%]
easy/q2889_reshape_data_pivot_test.py          [ 86%]
easy/q2890_reshape_data_melt_test.py           [ 93%]
easy/q2891_method_chaining_test.py             [100%]

===== 15 passed in 0.53s =====

Some Python basics

# Defining a function
def function_name(param_name: param_type) -> return_type:
    # code

# Comparing a tuple
assert (10, 5) == (rows, cols)

# Print something
print("message")