Skip to main content
PyPi version Python compatibility GitHub Actions Workflow Status AppVeyor status PyPi Libraries.io dependency status for latest release

massedit

formerly known as Python Mass Editor

Implements a python mass editor to process text files using Python code. The modification(s) is (are) shown on stdout as a diff output. One can then modify the target file(s) in place with the -w/–write option. This is very similar to 2to3 tool that ships with Python 3.

WARNING: A word of caution about the usage of eval()

This tool is useful as far as it goes but it does rely on the python eval() function and does not check the code being executed. It is a major security risk and one should not use this tool in a production environment.

See Ned Batchelder’s article for a thorough discussion of the dangers linked to eval() and ways to circumvent them. Note that None of the counter-measure suggested in the article are implemented at this time.

Usage

You probably will need to know the basics of the Python re module (regular expressions).

usage: massedit.py [-h] [-V] [-w] [-v] [-e EXPRESSIONS] [-f FUNCTIONS]
                   [-x EXECUTABLES] [-s START_DIRS] [-m MAX_DEPTH] [-o FILE]
                   [-g FILE] [--encoding ENCODING] [--newline NEWLINE]
                   [file pattern [file pattern ...]]

Python mass editor

positional arguments:
  file pattern          shell-like file name patterns to process or - to read
                        from stdin.

optional arguments:
  -h, --help            show this help message and exit
  -V, --version         show program's version number and exit
  -w, --write           modify target file(s) in place. Shows diff otherwise.
  -v, --verbose         increases log verbosity (can be specified multiple
                        times)
  -e EXPRESSIONS, --expression EXPRESSIONS
                        Python expressions applied to target files. Use the
                        line variable to reference the current line.
  -f FUNCTIONS, --function FUNCTIONS
                        Python function to apply to target file. Takes file
                        content as input and yield lines. Specify function as
                        [module]:?<function name>.
  -x EXECUTABLES, --executable EXECUTABLES
                        Python executable to apply to target file.
  -s START_DIRS, --start START_DIRS
                        Directory(ies) from which to look for targets.
  -m MAX_DEPTH, --max-depth-level MAX_DEPTH
                        Maximum depth when walking subdirectories.
  -o FILE, --output FILE
                        redirect output to a file
  -g FILE, --generate FILE
                        generate stub file suitable for -f option
  --encoding ENCODING   Encoding of input and output files
  --newline NEWLINE     Newline character for output files

Examples:
# Simple string substitution (-e). Will show a diff. No changes applied.
massedit.py -e "re.sub('failIf', 'assertFalse', line)" *.py

# File level modifications (-f). Overwrites the files in place (-w).
massedit.py -w -f fixer:fixit *.py

# Will change all test*.py in subdirectories of tests.
massedit.py -e "re.sub('failIf', 'assertFalse', line)" -s tests test*.py

# Will transform virtual methods (almost) to MOCK_METHOD suitable for gmock (see https://github.com/google/googletest).
massedit.py -e "re.sub(r'\s*virtual\s+([\w:<>,\s&*]+)\s+(\w+)(\([^\)]*\))\s*((\w+)*)(=\s*0)?;', 'MOCK_METHOD(\g<1>, \g<2>, \g<3>, (\g<4>, override));', line)" gmock_test.cpp

If massedit is installed as a package (from pypi for instance), one can interact with it as a command line tool:

python -m massedit -e "re.sub('assertEquals', 'assertEqual', line)" test.py

Or as a library (command line option above to be passed as kewyord arguments):

>>> import massedit
>>> filenames = ['massedit.py']
>>> massedit.edit_files(filenames, ["re.sub('Jerome', 'J.', line)"])

Lastly, there is a convenient massedit.bat wrapper for Windows included in the distribution.

Installation

Download massedit.py from http://github.com/elmotec/massedit or :

python -m pip install massedit

Poor man source-to-source manipulation

I find myself using massedit mostly for source to source modification of large code bases like this:

First create a fixer.py python module with the function that will process your source code. For instance, to add a header:

def add_header(lines, file_name):
    yield '// This is my header'  # will be the first line of the file.
    for line in lines:
        yield line

Adds the location of fixer.py to your $PYTHONPATH, then simply call massedit.py like this:

massedit.py -f fixer:add_header *.h

You can add the -s . option to process all the .h files reccursively.

Plans

  • Add support for 3rd party tool (e.g. autopep8) to process the files.

  • Add support for a file of expressions as an argument to allow multiple modification at once.

  • Find a satisfactory way (ie. easy to use) to handle multiline regex as the current version works on a line by line basis.

Rationale

  • I have a hard time practicing more than a few dialects of regular expressions.

  • I need something portable to Windows without being bothered by eol.

  • I believe Python is the ideal tool to build something more powerful than simple regex based substitutions.

Background

I have been using runsed and checksed (from Unix Power Tools) for years and did not find a good substitute under Windows until I came across Graham Fawcett python recipe 437932 on ActiveState. It inspired me to write the massedit.

The core was fleshed up a little, and here we are. If you find it useful and enhance it please, do not forget to submit patches. Thanks!

If you are more interested in awk-like tool, you probably will find pyp a better alternative.

Contributing

To set things up for development, please pip-install massedit as shown below. It will install it in editable mode and the develop extra packages, including commitizen that is recommended to have commits follow conventional commits convention:

python -m venv venv
. venv/bin/activate
python -m pip install -e .[develop,test]

License

Licensed under the term of MIT License. See attached file LICENSE.txt.

Changes

See CHANGELOG.md for changes later than 0.69.0

0.69.1 (2023-09-10)

Updated infrastructure files to setup.cfg/pyproject.toml instead of setup.py. Thanks @isidroas.

0.69.0 (2020-12-22)

Also moved CI to github workflows from travis and added regression tests for Python 2.7.

0.68.6 (2019-12-02)

Added support for Python 3.8, stdin input via - argument. Documented regex to turn base classes into googlemock MOCK_METHOD.

0.68.5 (2019-04-13)

Added –newline option to force newline output. Thanks @ALFNeT!

0.68.4 (2017-10-24)

Fixed bug that would cause changes to be missed when the -w option is ommited. Thanks @tgoodlet!

0.68.3 (2017-09-20)

Added –generate option to quickly generate a fixer.py template file to be modified to be used with -f fixer.fixit option. Added official support for Python 3.6

0.68.1 (2016-06-04)

Fixed encoding issues when processing non-ascii files. Added –encoding option to force the value of the encoding if need be. Listed support for Python 3.5

0.67.1 (2015-06-28)

Documentation fixes.

0.67 (2015-06-23)

Added file_name argument to processing functions. Fixed incorrect closing of sys.stdout/stderr. Improved diagnostic when the processing function does not take 2 arguments. Swapped -v and -V option to be consistent with Python. Pylint fixes. Added support for Python 3.4. Dropped support for Python 3.2.

0.66 (2013-07-14)

Fixed lost executable bit with -f option (thanks myint).

0.65 (2013-07-12)

Added -f option to execute code in a separate file/module. Added Travis continuous integration (thanks myint). Fixed python 2.7 support (thanks myint).

0.64 (2013-06-01)

Fixed setup.py so that massedit installs as a script. Fixed eol issues (thanks myint).

0.63 (2013-05-27)

Renamed to massedit. Previous version are still known as Python-Mass-Editor.

0.62 (2013-04-11)

Fixed bug that caused an EditorError to be raised when the result of the expression is an empty string.

0.61 (2012-07-06)

Added massedit.edit_files function to ease usage as library instead of as a command line tool (suggested by Maxim Veksler).

0.60 (2012-07-04)

Treats arguments as patterns rather than files to ease processing of multiple files in multiple subdirectories. Added -s (start directory) and -m (max depth) options.

0.52 (2012-06-05)

Upgraded for python 3. Still compatible with python 2.7.

0.51 (2012-05)

Initial release (Beta).

Contributor acknowledgement

https://github.com/myint https://github.com/tgoodlet https://github.com/ALFNeT https://github.com/isidroas

Metadata

Release files for massedit 0.71.0

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for massedit 0.71.0
File Size Uploaded Provenance
massedit-0.71.0.tar.gz 19.6 kB With provenance Details

Built distribution (wheel)

Table of built distributions (wheels) for massedit 0.71.0
File Interpreter ABI Platform
massedit-0.71.0-py3-none-any.whl Python 3 none any Details

Total release size: 33.3 kB

Release files / massedit-0.71.0.tar.gz

Download URL massedit-0.71.0.tar.gz
Size 19.6 kB
Tags Source
SHA-256 checksum
How to use checksums
6386eedd429ea547531faeb2061747b010c9fd0b59cfd028d6de08e01a100f73
BLAKE2b-256 checksum
How to use checksums
bfab54cb0d0e2d5ebc46aea89c0e4b9ec11f437faf14e50d3be43c5857cf897f
Upload date
Uploaded using Trusted Publishing?
What is trusted publishing?
Yes
Uploaded via twine/6.1.0 CPython/3.13.7

Provenance

Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.

PyPI Publish Attestation

PyPI verified that this artifact, at this checksum, originated from the publisher listed below.

Signed by GitHub Actions, verified by PyPI on Sep 21, 2025.

Transparency log

Release files / massedit-0.71.0-py3-none-any.whl

Download URL massedit-0.71.0-py3-none-any.whl
Size 13.7 kB
Tags Python 3
SHA-256 checksum
How to use checksums
4ac211fddd0c27fac784e545872cb906480072153b412b180565a3a273a332c9
BLAKE2b-256 checksum
How to use checksums
1a7212a5e322d7e74c36f318992f44fd392a20a860f90c10df936e054e76e406
Upload date
Uploaded using Trusted Publishing?
What is trusted publishing?
Yes
Uploaded via twine/6.1.0 CPython/3.13.7

Provenance

Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.

PyPI Publish Attestation

PyPI verified that this artifact, at this checksum, originated from the publisher listed below.

Signed by GitHub Actions, verified by PyPI on Sep 21, 2025.

Transparency log

Security for massedit 0.71.0

Provenance

Provenance describes where a file came from. On PyPI, provenance is shared via attestations, which provide a verifiable record of the build or publishing details. View details, limitations and caveats.

Full provenance

All 2 files in this release have been uploaded with provenance metadata.

Select from 2 files

Attestation for massedit-0.71.0.tar.gz

PyPI Publish Attestation

PyPI verified that this artifact, at this checksum, originated from the publisher listed below.

Signed by GitHub Actions, verified by PyPI on Sep 21, 2025.

Transparency log

A note on package security

PyPI is a repository for distributing packages, not a service for auditing them. While third-party security researchers and our staff do their best to detect and remove malicious packages, PyPI cannot guarantee the quality, security or suitability of any given package.

To learn more about protecting yourself from malicious actors, visit our package security documentation.

Anthropic, PBC Visionary sponsor Bloomberg Visionary sponsor Hudson River Trading Visionary sponsor Meta Visionary sponsor NVIDIA Visionary sponsor Microsoft Sustainability sponsor Depot Continuous Integration AWS Cloud computing and Security Sponsor Datadog Monitoring Fastly CDN Google Download Analytics Sentry Error logging StatusPage Status page