Python Curses Syntax Highlighting

A Python library for displaying syntax-highlighted code in terminal applications using Python's curses library and Pygments for lexical analysis.

Features

• Syntax Highlighting: Uses Pygments to support hundreds of programming languages
• File and String Input: Display a file by path or pass a string directly
• Efficient Large File Handling: Lazy loading with block-based caching
• Theme: Light/dark theme support
• Optional Features: Line numbers, indent guides, configurable display area, line wrapping or truncation
• Character Width Aware: Properly handles special characters using wcwidth

Installation

pip install curses-syntax-highlighting

Two Input Modes

Use preview_text when rendering files. Use preview_string when the code comes from a variable - fetched from an API, generated at runtime, stored in a database, etc.

Quick Start

import curses
from curses_syntax_highlighting import preview_text, preview_string

def main(stdscr):
    # From a file - lexer detected automatically
    preview_text(stdscr, 'example.py', show_line_numbers=True, theme='dark')
    stdscr.getch()

    # From a string - language supplied explicitly
    code = open('example.rs').read()
    preview_string(stdscr, code, language='rust', show_line_numbers=True)
    stdscr.getch()

curses.wrapper(main)

Both functions accept the same options: code_x, code_y, code_w, code_h, show_line_numbers, indent_guides, theme ('dark'/'light'), wrap, bg_color, scroll_offset. They return a viewer with a total_lines attribute useful for implementing scroll bounds.

Pure Renderer - No Key Stealing

The library never calls getch(). Every function is a draw call that renders and returns immediately, leaving all input handling to your application:

while True:
    preview_text(stdscr, filepath, scroll_offset=scroll)
    key = stdscr.getch()          # your app owns all input
    if key == curses.KEY_DOWN:
        scroll += 1

API Reference

High-Level Functions

preview_text(stdscr, filepath, **options) → LazyFileViewer

Display a syntax-highlighted file. Lexer is detected automatically. Loads lazily in blocks - suitable for large files. Returns None if the file is not found.

preview_string(stdscr, text, language=None, **options) → TextViewer

Display a syntax-highlighted string. language is a Pygments alias ('python', 'rust', 'javascript', …); pass None for plain text. The string is tokenized upfront and held in memory.

display_code(stdscr, viewer, token_to_color, code_x, code_y, code_w, code_h, show_line_numbers, indent_guides, scroll_offset=0, wrap=False)

Low-level renderer. Accepts any viewer with a get_lines(start, count) method and a total_lines attribute.

init_colors(theme_name='dark', start_color_id=200, bg_color=None)

Initialize curses color pairs for a theme. Must be called after curses.initscr(). Color pair IDs start at 200 by default, leaving 1–199 free for your application.

Classes

LazyFileViewer(filepath, lexer, block_size=50) · TextViewer(text, lexer)

Both expose get_lines(start, count) and total_lines. LazyFileViewer reads the file in blocks on demand; TextViewer tokenizes the full string upfront. Pass either to display_code().

get_lexer(filepath) · get_lexer_for_language(language)

Detect a lexer from a file path or a language alias respectively.

Themes

Two built-in themes: 'dark' and 'light'. Both default to the terminal's background color. Customize by editing THEMES in curses_syntax_highlighting/themes.py.

Requirements

• Python 3.7+
• pygments >= 2.0.0
• wcwidth >= 0.2.0