MCTS Crossword Generator

This package provides a pure Python implementation for generating crosswords using Monte Carlo Tree Search (MCTS).

• A good overview about the project can be found in this blog post.
• The pip package can be found on PyPI

Quickstart

A: Install package:

1. Create and activate a virtual environment based on Python >= 3.8
2. Install crossword_generator package:

pip install crossword-generator

B: Generate crossword with default settings:

You can generate a crossword without providing any arguments. This will fill a 4x5 layout without any black squares using words from an English dictionary.

To do so, activate your virtual environment and chose one of the following (equivalent) options:

1. Call application directly:

crossword

2. Execute package:

python -m crossword_generator

3. Run the main function in a python shell or your own script:

>>> from crossword_generator import generate_crossword
>>> generate_crossword()

For the next examples I assume you are using the first option to interact with the package.

Examples

• To get started and see which input formats are required, you can download some english (comma-separated) or german (semicolon-separated) sample data.
• Let's assume you have downloaded the sample files into a directory called "crossword_input" inside your working directory.

A: Use your own layouts

• In order to use your own layouts, you will need to set argument path_to_layout to a CSV file on your local machine.
• the CSV file must have an index column and a header row
• potential letters are marked with "_" (underscore)
• black squares are marked with "" (empty)

Fill an empty 5x12 layout:

crossword --path_to_layout "crossword_input/layout_5_12_empty.csv"

Fill a prefilled 5x12 layout:

crossword --path_to_layout "crossword_input/layout_5_12_prefilled.csv"

Fill an entire NYT-style 15x15 layout:

crossword --path_to_layout "crossword_input/layout_15_15_empty.csv"

Of course, you can also provide arguments from within your code:

generate_crossword(
  path_to_layout="crossword_input/layout_15_15_empty.csv",
)

B: Use your own words

• In order to use your own set of words, you will need to set argument path_to_words to a CSV file (or pattern of CSV files) on your local machine.
• the CSV file(s) must contain a column named "answer" with the relevant words

Fill an empty 5x12 layout with words from a list

crossword --path_to_layout "crossword_input/layout_5_12_empty.csv" --path_to_words "crossword_input/sample_words.csv"

Again, you can do the same from within your code:

generate_crossword(
  path_to_layout="crossword_input/layout_5_12_empty.csv",
  path_to_words="crossword_input/sample_words.csv",
)

C: Other arguments you might want to play with:

• num_rows & num_cols [int]
  • number of rows / columns the layout should have
  • will only be considered if path_to_layout is not specified
• max_num_words [int]
  • limits the number of words to improve runtime
• max_mcts_iterations [int]
  • sets the maximum number of MCTS iterations
  • can be increased to get a better solution or decreased to improve runtime
• random_seed [int]
  • change the seed to obtain different filled crosswords
• output_path [str]
  • if provided, save the final grid and a summary as CSV files into the provided directory

Modules

• optimizer.py
  • script that contains the main function generate_crossword()
• layout_handler.py
  • Provides the layout that will later be filled with words
  • NewLayoutHandler: creates a new layout from scratch
  • ExistingLayoutHandler: reads an existing layout from a CSV file
• word_handler.py
  • Provides the words that will later be filled into the layout
  • DictionaryWordHandler: get words from NLTK corpus
  • FileWordHandler: read words from CSV files
• state.py
  • Entry: class that represents the current state of one entry of the crossword
  • CrosswordState: class that represents the current state of whole crossword
• tree_search.py
  • TreeNode: represents one node of the MCTS tree
  • MCTS: represents the whole MCTS tree and provides all necessary functionalities such as
    • Selection
    • Expansion
    • Simulation / Rollout
    • Backpropagation

References & Dependencies

• The MCTS implementation in tree_search.py is based on the algorithm provided by pbsinclair42, which I adapted in several ways:
  • Convert from 2-player to 1-player domain
  • Adjust reward function + exploration term
  • Add additional methods to analyze the game tree
  • Use PEP 8 code style
• Have a look at pyproject.toml for a list of all required and optional dependencies
• Python >= 3.8
• Required packages
  • nltk>=3.5
  • pandas>=1.4.0
  • numpy>=1.22.0
  • tqdm>=4.41.0

Future work

• Add a python module that creates questions for given answers using NLP techniques
• Add a graphical user interface (GUI)