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October 07, 2020

Sourcery CLI

Sourcery CLI

Sourcery is now available as a command line interface. This enables several new use cases:

  • Refactor files on your machine without needing to run Sourcery through PyCharm or VSCode
  • Check every commit is refactored using a pre-commit hook
  • Run a continuous integration job to check all code is refactored

This functionality is only available with Pro/Team subscriptions. If you'd like to try it out for your team please contact us.


The Sourcery command line interface can be installed by running:

pip install sourcery


Once installed you can interactively login with:

sourcery login

which will open up a browser tab and ask for confirmation.


To display suggested refactorings as a diff:

sourcery refactor {file_or_directory}

And to apply those changes to the files:

sourcery refactor --in-place {file_or_directory}

Full documentation is available here.

Code quality metrics enabled by default in the IDE plugins

You can now hover over a method definition to see a quick view of its code quality. The metrics available are:

  • Cognitive complexity - a measure of how much complex nested logic is in the method
  • Size - a measure of how large the method is
  • Working memory - a measure of how many variables you need to keep in mind to understand the most complex parts of the method
  • Quality - a combination of the above metrics to give a percentage quality score

This can be switched off in the Sourcery section of the plugin settings.

New Refactorings

Use with context manager to ensure file closure

A common way of opening and using files is:

file = open("welcome.txt")
data =

However if an exception is thrown in between the file being opened and closed the call to file.close() may end up being skipped. By using Python's with context manager the file is closed for you as soon as the block is exited.

with open("welcome.txt") as file:
    data =

Extending the list-comprehension refactoring

We have now extended this refactoring to include an additional case, where augmented assignment is used to add to the list rather than append.

The following code:

files = []
for x in file_iterator:
    if x[-4:] == ".csv":
        files += [x]

will now be refactored as:

files = [x for x in file_iterator if x[-4:] == ".csv"]

Simplify if expression by using or

Often we find ourselves setting a value if it evaluates to True, and otherwise using a default.

currency = args["currency"] if args["currency"] else DEFAULT_CURRENCY

This can be simplified to the following, which is a bit easier to read and avoids the duplication of args['currency'].

currency = args["currency"] or DEFAULT_CURRENCY

Bug Fixes

  • Prevent use-assigned-variable from re-using properties