We push all new contributions to use type hints as discussed in CONTRIBUTING.md.
All efforts to add type hints to existing algorithms would be warmly received.

We can use mypy for testing code

We do this already https://github.com/TheAlgorithms/Python/blob/master/.travis.yml#L17

@cclauss How about a dev sprint kind of thing where we go about adding all such improvements?

Cool idea! Another thing (a sprint topic?) that is bugging me is code complexity which we currently set to 25 but I would be much happier to see it at 15. We would need to ensure that the files have strong type hints and tests before modifying them to reduce their cyclomatic complexity.

Another cool sprint topic would be to add doctests to Python files that have <10% test coverage. Some files like file_transfer/send_file.py and the web programming files are difficult to write tests for but others should be fair game.

Should we have a short sprint or a long one? One idea would be 24 hour sprint — given that tomorrow is summer solstice (longest day of the year) — the sprint could start at midnight tonight (in whatever timezone the contributer is in) and last for 24 hours. #2128 could be our tracking issue for keeping track of tasks and accomplishments. Thoughts on this Summer Solstice Special Sprint idea.

Seems awesome, we can gain some attention by Summer Solstice Special Sprint, I am up on gitter if you want to discuss

Another cool sprint topic would be to add doctests to Python files that have <10% test coverage. Some files like file_transfer/send_file.py and the web programming files are difficult to write tests for but others should be fair game.

Difficult but not impossible. We can create issue with some labels. Perhaps we find someone who will write tests or even code (for example simple server for response) for testing it 😃

Concerning complexity and maintainability, I've run the repo through wily (https://github.com/tonybaloney/wily), a command-line application for tracking, reporting on the complexity of Python tests and applications.

Here are the results for maintainability index [0..100] per module. The scale considers anything lower than 25 as hard to maintain, and anything over 75 as easy to maintain.

│ File                                                                    │   Maintainability Index │
│ hashes                                                                  │                 60.1865 │
│ neural_network                                                          │                 67.4381 │
│ ciphers                                                                 │                 67.8471 │
│ graphs                                                                  │                 68.9013 │
│ bit_manipulation                                                        │                 69.5657 │
│ linear_algebra                                                          │                 69.6743 │
│ searches                                                                │                 70.5201 │
│ backtracking                                                            │                 71.0636 │
│ divide_and_conquer                                                      │                 71.504  │
│ blockchain                                                              │                 71.9272 │
│ data_structures                                                         │                 71.9902 │
│ matrix                                                                  │                 72.5374 │
│ scripts                                                                 │                 73.9013 │
│ strings                                                                 │                 74.1231 │
│ machine_learning                                                        │                 75.3904 │
│ sorts                                                                   │                 75.6606 │
│ maths                                                                   │                 75.6964 │
│ other                                                                   │                 75.6972 │
│ traversals                                                              │                 76.3276 │
│ geodesy                                                                 │                 76.5739 │
│ dynamic_programming                                                     │                 76.6071 │
│ conversions                                                             │                 77.2626 │
│ boolean_algebra                                                         │                 78.4325 │
│ scheduling                                                              │                 78.8933 │
│ greedy_method                                                           │                 79.298  │
│ compression                                                             │                 80.0726 │
│ networking_flow                                                         │                 81.1551 │
│ arithmetic_analysis                                                     │                 83.0291 │
│ genetic_algorithm                                                       │                 83.2064 │
│ project_euler                                                           │                 83.7122 │
│ web_programming                                                         │                 84.3123 │
│ graphics                                                                │                 84.6733 │
│ computer_vision                                                         │                 84.8111 │
│ digital_image_processing                                                │                 86.2331 │
│ cellular_automata                                                       │                 87.3411 │
│ fuzzy_logic                                                             │                 87.7142 │
│ file_transfer                                                           │                 96.1178 │
│ quantum                                                                 │                100      │
│ images                                                                  │                100      │
│ Total                                                                   │                 77.2957 │

This allows us to track the overall maintainability of the repo (=77.3) and focus improvements on the less maintainable files. For new files, a threshold of 75 could be set for the maintainability index.

Please pick one directory (and ONLY one directory) [like hashes] and create a PR that demonstrates how we can improve.