pip-compile-multi 1.1.11

Compile multiple requirements files to lock dependency versions

Compile multiple requirements files to lock dependency versions

Installation

pip install pip-compile-multi

Basic Usage

pip-compile-multi

Example scenario

I will start from the very basics of dependency management and will go very slow, so if you feel bored, just scroll to the next section.

Suppose you have a python project with following direct dependencies:

click
pip-tools

(Yes I took pip-compile-multi as an example). Let’s save them as-is in requirements/base.in. Those are unpinned libraries, it means that whenever developer runs

pip install -r requirements/base.in

he will get some version of these libraries. And chances are that if several developers do the same over some period in time, some will have different dependency versions than others. Also, if the project is online service, one day it may stop working after redeployment because some of the dependencies had backward incompatible release. That kind of releases is more common than a newbie can think. More or less every package with a version higher than 2.0.0 had them.

To avoid this problem Python developers are hard-pinning (aka locking) their dependencies. So instead of a list of libraries, they have something like:

click==6.7
pip-tools==1.11.0

(To keep things neat let’s put this into requirements/base.txt) That’s good for a starter. But there are two important drawbacks:

1. Developers have to do non-trivial operations if they want to keep up with newer versions (that have bug fixes and performance improvements).

2. Indirect dependencies (that is dependencies of dependencies) may still have backward-incompatible releases, that brake everything.

Let’s put aside point 1 and fight point 2. Let’s do

pip freeze > requirements/base.txt

Now we have full heirarchy of dependencies hard-pinned:

click==6.7
first==2.0.1
pip-tools==1.11.0
six==1.11.0

That’s great, and solves the main problem - service will be deployed exactly [1] the same every single time and all developers will have identical environments.

This case is so common, that there already is a number of tools to solve it. Two worth mentioning are:

1. Pip Tools - a mature package that is enhanced by pip-compile-multi.

2. PipEnv - fresh approach that is going to become Python the standard way of locking dependencies some day.

But what if the project uses some packages that are not required by the service itself? For example pytest, that is needed to run unit tests, but should never be deployed to a production site. Or flake8 - syntax checking tool. If they are installed in the current virtual environment, they will get into pip freeze output. That’s no good. And removing them manually from requirements/base.txt is not an option. But still, these packages must be pinned to ensure, that tests are running the same way by the whole team (and build server).

So let’s get hands dirty and put all the testing stuff into requirements/test.in:

-r base.in

prospector
pylint
flake8
mock
six

Note, how I put -r base.in in the beginning, so that test dependencies are installed along with the base.

Now installation command is

pip install -e requirements/test.in

For one single time (exceptionally to show how unacceptable is this task) let’s manually compose requirements/test.txt. After installation, run freeze to bring the whole list of all locked packages:

$ pip freeze
astroid==1.6.0
click==6.7
dodgy==0.1.9
first==2.0.1
flake8==3.5.0
flake8-polyfill==1.0.2
isort==4.2.15
lazy-object-proxy==1.3.1
mccabe==0.6.1
mock==2.0.0
pbr==3.1.1
pep8-naming==0.5.0
pip-tools==1.11.0
prospector==0.12.7
pycodestyle==2.0.0
pydocstyle==2.1.1
pyflakes==1.6.0
pylint==1.8.1
pylint-celery==0.3
pylint-common==0.2.5
pylint-django==0.7.2
pylint-flask==0.5
pylint-plugin-utils==0.2.6
PyYAML==3.12
requirements-detector==0.5.2
setoptconf==0.2.0
six==1.11.0
snowballstemmer==1.2.1
wrapt==1.10.11

Wow! That’s quite a list! But we remember what goes into base.txt:

1. click

2. first

3. pip-tools

4. six

Good, everything else can be put into requirements/test.txt. But wait, six is included in test.in and is missing in test.txt. That feels wrong… Ah, it’s because we’ve moved six to the base.txt. It’s good, that we didn’t forget, that it should be in base. We might forget next time though.

Why don’t we automate it? That’s what pip-compile-multi is for.

Managing dependency versions in multiple environments

Let’s rehearse, example service has two groups of dependencies (or, as I call them, environments):

$ cat requirements/base.in
click
pip-tools

$ cat requirements/test.in
-r base.in
prospector
pylint
flake8
mock
six

To make automation even more appealing, let’s add one more environment. I’ll call it local - things that are needed during development, but are not required by tests, or service itself.

$ cat requirements/local.in
-r test.in
tox

Now we want to put all base dependencies along with all their recursive dependencies in base.txt, all recursive test dependencies except for base into test.txt, and all recursive local dependencies except for base and test into local.txt.

$ pip-compile-multi
Locking requirements/base.in to requirements/base.txt. References: []
Locking requirements/test.in to requirements/test.txt. References: ['base']
Locking requirements/local.in to requirements/local.txt. References: ['base', 'test']

Yes, that’s right. All the tedious dependency versions management job done with a single command, that doesn’t even have options.

Now you can run git diff to review the changes and git commit to save them. To install the new set of versions run:

pip install -Ur requirements/local.txt

It’s a perfect time to run all the tests and make sure, that updates were backward compatible enough for your needs. More often than I’d like in big projects, it’s not so. Let’s say new version of pylint dropped support of old Python version, that you still need to support. Than you open test.in and soft-pin it with descriptive comment:

$ cat requirements/test.in
-r base.in
prospector
pylint<1.8  # Newer versions dropped support for Python 2.4
flake8
mock
six

I know, this example is made up. But you get the idea. That re-run pip-compile-multi to compile new test.txt and check new set.

Benefits of using pip-compile-multi

I want to summarise, why you need to start using pip-compile-multi. Some of the benefits are achievable with other methods, but I want to be general:

1. Production will not suddenly brake after redeployment because of backward incompatible dependency release.

2. The whole team will use the same package versions and see the same outcomes. No more “works for me” and “I can not reproduce this” [2].

3. Service still uses most recent versions of packages. And fresh means best here.

4. Dependencies are upgraded when the time is suitable for the service, not whenever they are released.

5. Different environments are separated into different files.

6. *.in files are small and manageable because they store only direct dependencies.

7. *.txt files are exhaustive and precise (but you don’t need to edit them).

Features

pip-compile-multi supports a number of options to customize compilation.

Requirements Directory

While it’s a common practice to put requirements files inside requirements directory, it’s not always the case. The directory can be overridden with this option:

-d, --directory TEXT   Directory path with requirements files

Requirements Files Extensions

By default pip-compile-multi compiles *.txt from *.in files. While it’s a sane choice, each project can use it’s own:

-i, --in-ext TEXT      File extension of input files
-o, --out-ext TEXT     File extension of output files

Compatible Releases

PEP-440 describes compatible release operator ~=. Sometimes it’s useful to have some of the dependencies pinned using this operator. For example, rapidly changing internal libraries. Format for this option is

-c, --compatible TEXT

where TEXT is a glob pattern for library name. This option can be supplied multiple times.

Generate hashes

Put package hash after pinned version for additional security. Format for this option is

-g, --generate-hashes TEXT  Environment name (base, test, etc) that needs
                            packages hashes. Can be supplied multiple times.

Example invocation:

$ pip-compile-multi -g base -g docs

Example output:

pip-tools==1.11.0 \
    --hash=sha256:50288eb066ce66dbef5401a21530712a93c659fe480c7d8d34e2379300555fa1 \
    --hash=sha256:ba427b68443466c389e3b0b0ef55f537ab39344190ea980dfebb333d0e6a50a3
first==2.0.1 \
    --hash=sha256:3bb3de3582cb27071cfb514f00ed784dc444b7f96dc21e140de65fe00585c95e \
    --hash=sha256:41d5b64e70507d0c3ca742d68010a76060eea8a3d863e9b5130ab11a4a91aa0e \
    # via pip-tools

pip requires all packages to have hashes if at least one has it. pip-compile-multi will recursively propagate this option to all environments that are referencing or referenced by passed environment name.

Custom Header

pip-compile-multi adds a brief header into generated files. Override it with

-h, --header TEXT      File path with custom header text for generated files

Limit .in files

By default pip-compile-multi compiles all .in files in requirements directory. To limit compilation to only a subset, use

-n, --only-name TEXT        Compile only for passed environment names and
                            their references. Can be supplied multiple
                            times.

For example, to compile one file under Python2.7 and another under Python3.6, run:

$ virtual-env27/bin/pip-compile-multi -n deps27
Locking requirements/deps27.in to requirements/deps27.txt. References: []
$ virtual-env36/bin/pip-compile-multi -n deps36
Locking requirements/deps36.in to requirements/deps36.txt. References: []

Check that pip-compile-multi was run after changes in .in file.

pip-compile-multi adds a special line (before header) in the beginning of each generated file. This line contains a SHA1 hash of the .in file’s contents.

Command

$ pip-compile-multi verify
Verifying that requirements/base.txt was generated from requirements/base.in.
Success - comments match.
Verifying that requirements/test.txt was generated from requirements/test.in.
Success - comments match.
Verifying that requirements/local.txt was generated from requirements/local.in.
Success - comments match.

recalculates hashes for .in files and compares them with the stored values.

If verification fails, an error message is logged and exit code 1 is returned:

$ pip-compile-multi verify
Verifying that requirements/base.txt was generated from requirements/base.in.
Success - comments match.
Verifying that requirements/test.txt was generated from requirements/test.in.
FAILURE!
Expecting: # SHA1:c93d71964e14b04f3c8327d16dbc4d6b1bbc3b1d
Found:     # SHA1:6c2562322ca1bdc8309b08581a2aa4efbb5a4534
Verifying that requirements/local.txt was generated from requirements/local.in.
Success - comments match.

Have fun!

Now that occasional backward incompatible dependancy release can’t ruin your day, you can spread the word about pip-compile-multi, ask for a new feature in a GitHub issue, or even open a PR ;-).

[1] That’s not really true. Someone could re-upload broken package under existing version on PyPI.

[2] Yeah, yeah, there are still a lot of ways to have these problems.

History

1.1.11 (2018-02-09)

• Propagate –only-name option to references

• Fixed extension override options

1.1.10 (2018-02-09)

• Added --generate-hashes option

1.1.9 (2018-02-08)

• Fixed directory override option

• Added –only-name option

1.1.8 (2018-01-25)

• Fixed comment justification

1.1.6 (2018-01-19)

• Added pip-compile-multi verify command

1.1.5 (2018-01-16)

• Omit future[s] packages for Python3

1.1.0 (2018-01-12)

• Added files discovery.

1.0.0 (2018-01-11)

• First release on PyPI.