isabella232 / slicker

a tool for moving things in python

Slicker: A Tool for Moving Things in Python

If you've ever tried to move a function or class in python, you'll find it's kind of a pain: you have to not only move the definition (and its imports, etc.) but also update references across the codebase. Slicker is a tool for doing just that!

Note: At this time Slicker is Python 2 only.

Installation

pip2 install slicker

Usage

To move a function myfunc defined in foo/bar.py to foo/baz.py:

slicker foo.bar.myfunc foo.baz.myfunc

The same syntax works if myfunc is instead a constant or class (although I sure hope you didn't name a class myfunc!). It also works if you want to change the name of myfunc:

slicker foo.bar.myfunc foo.bar.new_name_for_myfunc

(And you can also make both changes at once, in the natural way.)

To move an entire module foo/bar.py to foo/baz.py you can do similarly:

slicker foo.bar foo.baz

or use filenames like:

slicker foo/bar.py foo/baz.py

You can also move a symbol into an existing module, or a module into an existing directory, just like mv. So this is equivalent to the first example:

slicker foo.bar.myfunc foo.baz

And to move foo/bar.py to a new file newfoo/bar.py in an existing directory newfoo/, you could do

slicker foo.bar newfoo  # (or slicker foo/bar.py newfoo/)

Using this syntax, you can also specify multiple things to move, so you could move both foo/bar.py and foo/baz.py to newfoo/ with

slicker foo/bar.py foo/baz.py newfoo/

You can tell slicker to use an alias when adding imports using -a/--alias:

slicker foo.bar.myfunc foo.baz.myfunc --alias baz

in which case slicker will add from foo import baz everywhere instead of import foo.baz. (You could also have used --alias foobaz in which case we would have done import foo.baz as foobaz.)

If you prefer to move the actual definition yourself, and just have slicker update the references, you can pass --no-automove. It's probably best to run slicker after doing said move.

For a full list of options, run slicker --help.

Frequently and Infrequently Asked Questions

What does slicker mean if it says "This import may be used implicitly."?

If you do import foo.bar, and some other file (perhaps another one you import) does import foo.baz, then your foo now also has a foo.baz, and so you can do foo.baz.func() with impunity, even though no import in your file directly mentions that module. (This is because foo in both files refers to the same object -- a.k.a. sys.modules['foo'] -- and so when the other file does import foo.baz it attaches baz to that shared object.) So if you've asked slicker to move foo.bar to newfoo.bar, when updating this file, it would like to replace the import foo.bar with import newfoo.bar, but it can't -- you're actually still using the import. So it will warn you of this case, and let you sort things out by hand.

Slicker left me with a bunch of misindented or long lines!

Yep, we don't fix these correctly (yet). Your linter should tell you what to fix, though.

Why is it called slicker?

Because pythons slither to move around, but this way is, uh, slicker. Which is to say: it seemed like a good idea at the time and as far as I could tell the name wasn't already taken.

How does it work?

See the blog post for an overview. If that's not enough, bug the authors or read the source!

Why don't you just use PyCharm or rope?

Good question -- we tried! Both are great projects and do a lot of things slicker doesn't; if they work for you then definitely use them. But for us, they were a little buggy and didn't fit our workflow. For more details, see the blog post.

Why don't you just use codemod or sed/perl?

Good question -- we tried! But it takes a lot of gluing things together to figure out all the right references to fix up in each file. And there's basically no hope of doing the right thing when fixing up string-references. We needed something that knew what python imports mean and could handle their special cases.

Changelog

0.9.3

• Fix description on PyPI, again

0.9.2

• Fix description on PyPI

0.9.1

• Handle relative imports correctly
• Lots of internal refactoring

0.9

• Initial release to PyPI