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python_readme.html
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<!DOCTYPE html>
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Python
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Python Projects with Pants
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<li class="toc-h1"><a href="#build-for-tests">BUILD for Tests</a></li>
<li class="toc-h1"><a href="#handling-python_requirement">Handling python_requirement</a></li>
<li class="toc-h1"><a href="#pex-contents">PEX Contents</a></li>
<li class="toc-h1"><a href="#interactive-console-with-repl-goal">Interactive Console with repl Goal</a></li>
<li class="toc-h1"><a href="#python_binary-entry_point">python_binary entry_point</a></li>
<li class="toc-h1"><a href="#more-about-python-tests">More About Python Tests</a></li>
<li class="toc-h2"><a href="#code-coverage">Code Coverage</a></li>
<li class="toc-h2"><a href="#interactive-debugging-on-test-failure">Interactive Debugging on Test Failure</a></li>
<li class="toc-h1"><a href="#building-a-setuppy-distutils-package">Building a setup.py Distutils Package</a></li>
<li class="toc-h1"><a href="#manipulating-pex-behavior-with-environment-variables">Manipulating PEX behavior with environment variables</a></li>
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<h1 id="python-projects-with-pants">Python Projects with Pants</h1>
<p>Pants makes the manipulation and distribution of hermetically sealed
Python environments painless. You can organize your code in the
<a href="first_concepts.html">Pants way</a>
with targets for binaries, libraries, and
tests. Pants builds Python code into
<a href="https://github.com/pantsbuild/pex/blob/master/docs/whatispex.rst">PEXes</a>.
(A PEX is, roughly, an archive file containing a runnable Python
environment.) Pants isn't the only PEX-generation tool out there; but if
you have some "common code" used by more than one PEX, Pants makes it
easy to manage the dependencies.</p>
<p>This page assumes that you've already read
<a href="first_tutorial.html">the Pants Tutorial</a>.</p>
<h2 id="relevant-goals-and-targets">Relevant Goals and Targets</h2>
<p><strong>Runnable Binary</strong></p>
<blockquote>
<p>Pants can generate PEXes, executables built from Python. Invoke the
<a href="options_reference.html#oref_goal_binary" pantsref="oref_goal_binary"><code>binary</code></a> goal on a
<a href="build_dictionary.html#bdict_python_binary" pantsref="bdict_python_binary"><code>python_binary</code></a> target to generate a <code>.pex</code>.
You can also invoke the
<a href="options_reference.html#oref_goal_run" pantsref="oref_goal_run"><code>run</code></a> goal on a
<code>python_binary</code> to run its code "in place."</p>
</blockquote>
<p><strong>Importable Code</strong></p>
<blockquote>
<p><a href="build_dictionary.html#bdict_python_library" pantsref="bdict_python_library"><code>python_library</code></a> BUILD targets make Python
code "import-able". The rule of thumb is that each directory of <code>.py</code>
files has a <code>BUILD</code> file with a <code>python_library</code> target. A Python
target that has a <code>python_library</code> in its <code>dependencies</code> can import
its code.</p>
<p>To use code that's not in your workspace, use a
<a href="build_dictionary.html#bdict_python_requirement_library" pantsref="bdict_python_requirement_library"><code>python_requirement_library</code></a>
and a
<a href="build_dictionary.html#bdict_python_requirement" pantsref="bdict_python_requirement"><code>python_requirement</code></a> to refer to
the code. To use several several of these via a <code>pip</code>-style
<code>requirements.txt</code> file, use a
<a href="build_dictionary.html#bdict_python_requirements" pantsref="bdict_python_requirements"><code>python_requirements</code></a>.
For details, see <a href="3rdparty_py.html">Python 3rdparty Pattern</a>.</p>
</blockquote>
<p><strong>Tests</strong></p>
<blockquote>
<p>A <a href="build_dictionary.html#bdict_python_tests" pantsref="bdict_python_tests"><code>python_tests</code></a> BUILD target has some <code>pytest</code> tests.
It normally depends on a <code>python_library</code> target so it can import and test the library's code.
Use the <a href="options_reference.html#oref_goal_test" pantsref="oref_goal_test"><code>test</code></a> goal to run these tests.</p>
</blockquote>
<p><strong>Generated Code</strong></p>
<blockquote>
<p>A <a href="build_dictionary.html#bdict_python_thrift_library" pantsref="bdict_python_thrift_library"><code>python_thrift_library</code></a> generates
Python code from <code>.thrift</code> source; a Python target that has this
target in its <code>dependencies</code> can <code>import</code> the generated Python code.</p>
</blockquote>
<h2 id="build-for-a-simple-binary">BUILD for a Simple Binary</h2>
<p>The pantsbuild/pants repo has a simple "hello world" sample Python
binary. You can use <code>binary</code> to build a PEX from it. You can then
run the PEX:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants binary examples/src/python/example/hello/main
...much output...
<span class="nv">$ </span>./dist/main.pex <span class="c"># run the generated PEX</span>
Hello, world!
<span class="nv">$ </span>./dist/main.pex Whirled
Hello, Whirled!
<span class="err">$</span>
</pre></div>
<p>You can also run the binary "from source" with the <code>run</code> goal:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants run.py --args<span class="o">=</span><span class="s1">'Whirled'</span> examples/src/python/example/hello/main
...much output...
14:32:01 00:00 <span class="o">[</span>py<span class="o">]</span>
14:32:02 00:01 <span class="o">[</span>run<span class="o">]</span>
Hello, Whirled!
14:32:02 00:01 <span class="o">[</span>jvm<span class="o">]</span>
SUCCESS
<span class="err">$</span>
</pre></div>
<p><a href="https://github.com/pantsbuild/pants/blob/master/examples/src/python/example/hello/main/BUILD"><code>examples/src/python/example/hello/main/BUILD</code></a>
defines a <code>python_binary</code> target, a build-able thing that defines a runnable program made from
Python code:</p>
<p>
<div class="md-included-snippet"><div class="codehilite"><pre><span class="n">python_binary</span><span class="p">(</span>
<span class="n">dependencies</span><span class="o">=</span><span class="p">[</span>
<span class="s">'examples/src/python/example/hello/greet:greet'</span><span class="p">,</span>
<span class="p">],</span>
<span class="n">source</span><span class="o">=</span><span class="s">'main.py'</span><span class="p">,</span>
<span class="p">)</span>
</pre></div></div>
</p>
<p>This binary has a source file, <code>main.py</code>, with its "main". A Python binary's "main" can be in a
depended-upon <code>python_library</code> or in the <code>python_binary</code>'s <code>source</code>. (Notice that's <code>source</code>,
not <code>sources</code>; a binary can have only one source file. If you want more, put them in a
<code>python_library</code> and let the <code>python_binary</code> depend on that.)</p>
<p>
<div class="md-included-snippet"><div class="codehilite"><pre><span class="k">if</span> <span class="n"><strong>name</strong></span> <span class="o">==</span> <span class="s">'<strong>main</strong>'</span><span class="p">:</span>
<span class="n">greetees</span> <span class="o">=</span> <span class="n">sys</span><span class="o">.</span><span class="n">argv</span><span class="p">[</span><span class="mi">1</span><span class="p">:]</span> <span class="ow">or</span> <span class="p">[</span><span class="s">'world'</span><span class="p">]</span>
<span class="k">for</span> <span class="n">greetee</span> <span class="ow">in</span> <span class="n">greetees</span><span class="p">:</span>
<span class="k">print</span><span class="p">(</span><span class="n">greet</span><span class="p">(</span><span class="n">greetee</span><span class="p">))</span>
</pre></div></div>
</p>
<p>This code imports code from another target. To make this work, the
binary target has a dependency <code>examples/src/python/example/hello/greet</code>
and the Python code can thus import things from <code>example.hello.greet</code>.</p>
<p>You remember that libraries configure "importable" code;
<code>example/hello/greet/BUILD</code> has a <code>python_library</code>:</p>
<p>
<div class="md-included-snippet"><div class="codehilite"><pre><span class="n">python_library</span><span class="p">(</span>
<span class="n">dependencies</span><span class="o">=</span><span class="p">[</span>
<span class="s">'3rdparty/python:ansicolors'</span><span class="p">,</span>
<span class="p">],</span>
<span class="p">)</span>
</pre></div></div>
</p>
<p>This <code>python_library</code> pulls in <code>greet.py</code>'s Python code:</p>
<p>
<div class="md-included-snippet"><div class="codehilite"><pre><span class="kn">from</span> <span class="nn">colors</span> <span class="kn">import</span> <span class="n">green</span>
<span class="k">def</span> <span class="nf">greet</span><span class="p">(</span><span class="n">greetee</span><span class="p">):</span>
<span class="sd">"""Given the name, return a greeting for a person of that name."""</span>
<span class="k">return</span> <span class="n">green</span><span class="p">(</span><span class="s">'Hello, {}!'</span><span class="o">.</span><span class="n">format</span><span class="p">(</span><span class="n">greetee</span><span class="p">))</span>
</pre></div></div>
</p>
<h2 id="build-for-tests">BUILD for Tests</h2>
<p>To test the library's code, we set up
<a href="https://github.com/pantsbuild/pants/blob/master/examples/tests/python/example_test/hello/greet/BUILD"><code>examples/tests/python/example_test/hello/greet/BUILD</code></a>
with a <code>python_tests</code> target. It depends on the library:</p>
<p>
<div class="md-included-snippet"><div class="codehilite"><pre><span class="n">python_tests</span><span class="p">(</span>
<span class="n">dependencies</span><span class="o">=</span><span class="p">[</span>
<span class="s">'examples/src/python/example/hello/greet:greet'</span><span class="p">,</span>
<span class="s">':prep'</span><span class="p">,</span>
<span class="p">],</span>
<span class="p">)</span>
<span class="c"># Prepare for the 'greet' test. Realistically, you wouldn't set up a</span>
<span class="c"># prep_command just to create an emtpy temp file. This is meant as a</span>
<span class="c"># simple example.</span>
<span class="n">prep_command</span><span class="p">(</span><span class="n">name</span><span class="o">=</span><span class="s">'prep'</span><span class="p">,</span>
<span class="n">prep_executable</span><span class="o">=</span><span class="s">'touch'</span><span class="p">,</span>
<span class="n">prep_args</span><span class="o">=</span><span class="p">[</span><span class="s">'/tmp/prep_command_result'</span><span class="p">]</span>
<span class="p">)</span>
</pre></div></div>
</p>
<p>Use <code>test</code> to run the tests. This uses <code>pytest</code>:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants <span class="nb">test </span>examples/tests/python/example_test/hello/greet
13:29:28 00:00 <span class="o">[</span>main<span class="o">]</span>
<span class="o">(</span>To run a reporting server: ./pants server<span class="o">)</span>
13:29:28 00:00 <span class="o">[</span>bootstrap<span class="o">]</span>
13:29:28 00:00 <span class="o">[</span>setup<span class="o">]</span>
13:29:28 00:00 <span class="o">[</span>parse<span class="o">]</span>
...
13:29:29 00:01 <span class="o">[</span><span class="nb">test</span><span class="o">]</span>
13:29:29 00:01 <span class="o">[</span>pytest<span class="o">]</span>
13:29:29 00:01 <span class="o">[</span>run<span class="o">]</span>
<span class="o">==============</span> <span class="nb">test </span>session <span class="nv">starts</span> <span class="o">===============</span>
platform darwin -- Python 2.6.8 -- py-1.4.20 -- pytest-2.5.2
plugins: cov, timeout
collected 2 items
examples/tests/python/example_test/hello/greet/test_greet.py ..
<span class="o">============</span> 1 passed in 0.02 <span class="nv">seconds</span> <span class="o">============</span>
13:30:18 00:50 <span class="o">[</span>junit<span class="o">]</span>
13:30:18 00:50 <span class="o">[</span>specs<span class="o">]</span>
SUCCESS
<span class="err">$</span>
</pre></div>
<h2 id="handling-python_requirement">Handling <code>python_requirement</code></h2>
<p><code>BUILD</code> files specify outside Python dependencies via
<a href="build_dictionary.html#bdict_python_requirements" pantsref="bdict_python_requirements"><code>python_requirements</code></a> and a
<code>requirements.txt</code> file and/or
<a href="build_dictionary.html#bdict_python_requirement_library" pantsref="bdict_python_requirement_library"><code>python_requirement_library</code></a> targets wrapping
<a href="build_dictionary.html#bdict_python_requirement" pantsref="bdict_python_requirement"><code>python_requirement</code></a>s.</p>
<p>Pants handles these dependencies for you. It never installs anything
globally. Instead, it builds the dependencies, caches them in <code>.pants.d</code>,
and assembles them <em>a la carte</em> into an execution environment.</p>
<h2 id="pex-contents">PEX Contents</h2>
<p>To build a PEX, invoke <code>./pants binary</code> on a <code>python_binary</code>
target:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants binary examples/src/python/example/hello/main
...
SUCCESS
<span class="nv">$ </span>./dist/main.pex
Hello, world!
</pre></div>
<p>Though the binary itself specifies just one dependency, the transitive
closure of hello/main's dependencies pulled in hello/greet and, in turn,
hello/greet's dependencies. Pants bundles up the closed set of all
dependencies into into the PEX.</p>
<h2 id="interactive-console-with-repl-goal">Interactive Console with <code>repl</code> Goal</h2>
<p>Use the <a href="options_reference.html#oref_goal_repl" pantsref="oref_goal_repl"><code>repl</code></a> goal with a Python target to run an interactive
Python REPL session.
Within the session, you can <code>import</code> the target's code and the code of its dependencies.</p>
<p>To drop into our example library target <code>examples/src/python/example/hello/greet</code> with verbosity
turn on to see what's going on in the background:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants -ldebug repl examples/src/python/example/hello/greet
15:11:41 00:00 <span class="o">[</span>main<span class="o">]</span>
<span class="o">(</span>To run a reporting server: ./pants server<span class="o">)</span>
...lots of build output...
15:11:42 00:01 <span class="o">[</span>repl<span class="o">]</span>
15:11:42 00:01 <span class="o">[</span>python-repl<span class="o">]</span>Building chroot <span class="k">for</span> <span class="o">[</span>PythonLibrary<span class="o">(</span>BuildFileAddress<span class="o">(</span>/Users/lhosken/workspace/pants/examples/src/python/example/hello/greet/BUILD, greet<span class="o">))]</span>:
Dumping library: PythonLibrary<span class="o">(</span>BuildFileAddress<span class="o">(</span>/Users/lhosken/workspace/pants/examples/src/python/example/hello/greet/BUILD, greet<span class="o">))</span>
Dumping requirement: <span class="nv">ansicolors</span><span class="o">==</span>1.0.2
Dumping distribution: .../ansicolors-1.0.2-py2-none-any.whl
15:11:42 00:01 <span class="o">[</span>run<span class="o">]</span>
Python 2.7.5 <span class="o">(</span>default, Mar 9 2014, 22:15:05<span class="o">)</span>
<span class="o">[</span>GCC 4.2.1 Compatible Apple LLVM 5.0 <span class="o">(</span>clang-500.0.68<span class="o">)]</span> on darwin
Type <span class="s2">"help"</span>, <span class="s2">"copyright"</span>, <span class="s2">"credits"</span> or <span class="s2">"license"</span> <span class="k">for </span>more information.
<span class="o">(</span>InteractiveConsole<span class="o">)</span>
>>>
</pre></div>
<p>Pants loads <code>ansicolors</code> (<code>greet</code>'s 3rdparty dependency). It would have
fetched this dependency over the network if necessary. (It wasn't
necessary to download <code>ansicolors</code>; Pants had already fetched it while
"bootstrapping" itself.)</p>
<p>To convince yourself that the environment contains <code>greet</code>'s dependencies, you can inspect
<code>sys.path</code> and import libraries:</p>
<div class="codehilite"><pre><span class="o">>>></span> <span class="kn">from</span> <span class="nn">example.hello.greet.greet</span> <span class="kn">import</span> <span class="n">greet</span>
<span class="o">>>></span> <span class="n">greet</span><span class="p">(</span><span class="s">"escape codes"</span><span class="p">)</span>
<span class="s">u'</span><span class="se">\x1b</span><span class="s">[32mHello, escape codes!</span><span class="se">\x1b</span><span class="s">[0m'</span>
<span class="o">>>></span> <span class="kn">from</span> <span class="nn">colors</span> <span class="kn">import</span> <span class="n">red</span>
<span class="o">>>></span> <span class="n">red</span><span class="p">(</span><span class="s">"other escape codes"</span><span class="p">)</span>
<span class="s">'</span><span class="se">\x1b</span><span class="s">[31mother escape codes</span><span class="se">\x1b</span><span class="s">[0m'</span>
</pre></div>
<p><strong>Dependencies built by Pants are never installed globally</strong>. These
dependencies only exist for the duration of the Python interpreter
forked by Pants.</p>
<h2 id="python_binary-entry_point"><code>python_binary</code> <code>entry_point</code></h2>
<p>An advanced feature of <code>python_binary</code> targets, you may in addition
specify direct entry points into PEX files rather than a source file.
For example, if we wanted to build an a la carte fab wrapper for fabric:</p>
<div class="codehilite"><pre><span class="n">python_binary</span><span class="p">(</span><span class="n">name</span> <span class="o">=</span> <span class="s">"fab"</span><span class="p">,</span>
<span class="n">entry_point</span> <span class="o">=</span> <span class="s">"fabric.main:main"</span><span class="p">,</span>
<span class="n">dependencies</span> <span class="o">=</span> <span class="p">[</span>
<span class="s">"3rdparty/python:fabric"</span><span class="p">,</span>
<span class="p">]</span>
<span class="p">)</span>
</pre></div>
<p>We build:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants src/python/fabwrap:fab
...
Wrote /private/tmp/wickman-pants/dist/fab.pex
</pre></div>
<p>And now dist/fab.pex behaves like a standalone fab binary:</p>
<div class="codehilite"><pre><span class="nv">$ </span>dist/fab.pex -h
Usage: fab <span class="o">[</span>options<span class="o">]</span> <<span class="nb">command</span>><span class="o">[</span>:arg1,arg2<span class="o">=</span>val2,host<span class="o">=</span>foo,hosts<span class="o">=</span><span class="s1">'h1;h2'</span>,...<span class="o">]</span> ...
Options:
-h, --help show this <span class="nb">help </span>message and <span class="nb">exit</span>
-d NAME, --display<span class="o">=</span>NAME
print detailed info about <span class="nb">command </span>NAME
-F FORMAT, --list-format<span class="o">=</span>FORMAT
formats --list, choices: short, normal, nested
-l, --list print list of possible commands and <span class="nb">exit</span>
--set<span class="o">=</span><span class="nv">KEY</span><span class="o">=</span>VALUE,... comma separated <span class="nv">KEY</span><span class="o">=</span>VALUE pairs to <span class="nb">set </span>Fab env vars
--shortlist <span class="nb">alias </span><span class="k">for</span> -F short --list
-V, --version show program<span class="s1">'s version number and exit</span>
<span class="s1"> -a, --no_agent don'</span>t use the running SSH agent
-A, --forward-agent forward <span class="nb">local </span>agent to remote end
--abort-on-prompts abort instead of prompting <span class="o">(</span><span class="k">for </span>password, host, etc<span class="o">)</span>
...
</pre></div>
<h2 id="more-about-python-tests">More About Python Tests</h2>
<p>Pants runs Python tests with <code>pytest</code>. You can pass CLI options to <code>pytest</code> with
<code>test.pytest --options</code>. For example, to only run tests whose names contain <code>req</code>,
you could run:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants test.pytest --options<span class="o">=</span><span class="s1">'-k req'</span> examples/tests/python/example_test/hello/greet
...
<span class="o">==============</span> <span class="nb">test </span>session <span class="nv">starts</span> <span class="o">===============</span>
platform darwin -- Python 2.6.8 -- py-1.4.20 -- pytest-2.5.2
plugins: cov, timeout
collected 2 <span class="nv">items</span>
<span class="o">=========</span> 2 tests deselected by <span class="s1">'-kfoo'</span> <span class="o">==========</span>
<span class="o">==========</span> 2 deselected in 0.01 <span class="nv">seconds</span> <span class="o">==========</span>
13:34:28 00:02 <span class="o">[</span>junit<span class="o">]</span>
13:34:28 00:02 <span class="o">[</span>specs<span class="o">]</span>
SUCCESS
</pre></div>
<p>You can pass CLI options to <code>pytest</code> via passthrough parameters if <code>test.pytest</code> is the last goal
and task on your command line. E.g., to run only tests whose names contain <code>req</code> via passthrough
parameters:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants test.pytest examples/tests/python/example_test/hello/greet -- -k req
...lots of build output...
10:43:04 00:01 <span class="o">[</span><span class="nb">test</span><span class="o">]</span>
10:43:04 00:01 <span class="o">[</span>run_prep_command<span class="o">]</span>
10:43:04 00:01 <span class="o">[</span>prep_command<span class="o">]</span>
10:43:04 00:01 <span class="o">[</span>pytest<span class="o">]</span>
10:43:04 00:01 <span class="o">[</span>run<span class="o">]</span>
<span class="o">==============</span> <span class="nb">test </span>session <span class="nv">starts</span> <span class="o">===============</span>
platform darwin -- Python 2.7.5 -- py-1.4.26 -- pytest-2.6.4
plugins: cov, timeout
collected 2 items
examples/tests/python/example_test/hello/greet/test_greet.py .
<span class="o">=========</span> 1 tests deselected by <span class="s1">'-kreq'</span> <span class="o">==========</span>
<span class="o">=====</span> 1 passed, 1 deselected in 0.05 <span class="nv">seconds</span> <span class="o">=====</span>
10:43:05 00:02 <span class="o">[</span>junit<span class="o">]</span>
10:43:05 00:02 <span class="o">[</span>specs<span class="o">]</span>
SUCCESS
</pre></div>
<p>...and to "unsilence" py.test (not suppress stderr and stdout), pass <code>-- -s</code>:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants test.pytest examples/tests/python/example_test/hello/greet -- -s
</pre></div>
<p>...and to remind yourself of py.test's help:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants test.pytest examples/tests/python/example_test/hello/greet -- -h
</pre></div>
<h3 id="code-coverage">Code Coverage</h3>
<p>To get code coverage data, set the <code>--coverage</code> flag in <code>test.pytest</code> scope.</p>
<p>The value of the flag is a comma-separated list of names of python packages or directories
containing code to measure coverage against. It can also take the special value <code>auto</code>, which
will cause Pants to attempt to deduce what to measure coverage against.</p>
<p>This auto-deduction examines the <code>coverage</code> attribute on each <code>python_tests</code>
target, which should be a list of packages. If a target has no <code>coverage</code> attribute,
Pants uses the package containing the test code. This is of course only useful if the
code under test lives in the same package as the code that tests it.</p>
<p>If you do specify package or directory names with <code>--coverage</code>, this overrides any <code>coverage</code>
attributes on <code>python_tests</code> targets.</p>
<p>For example:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants test.pytest --coverage<span class="o">=</span>example.hello.greet,example.hello.main examples/tests/python/example_test/hello/greet
...lots of build output...
<span class="o">============</span> 2 passed in 0.22 <span class="nv">seconds</span> <span class="o">============</span>
Name Stmts Miss Branch BrMiss Cover
------------------------------------------------------------------------------------
examples/src/python/example/hello/greet/__init__ 0 0 0 0 100%
examples/src/python/example/hello/greet/greet 4 0 0 0 100%
------------------------------------------------------------------------------------
TOTAL 4 0 0 0 100%
</pre></div>
<p>This measures coverage against all python code in <code>example.hello.greet</code> and <code>example.hello.main</code>.</p>
<p>Similarly, a list of directories can be specified (either absolute or relative to the build root):</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants test.pytest --coverage<span class="o">=</span>example/hello examples/tests/python/example_test/hello/greet
...lots of build output...
<span class="o">============</span> 2 passed in 0.23 <span class="nv">seconds</span> <span class="o">============</span>
Name Stmts Miss Branch BrMiss Cover
------------------------------------------------------------------------------------
examples/src/python/example/hello/__init__ 0 0 0 0 100%
examples/src/python/example/hello/greet/__init__ 0 0 0 0 100%
examples/src/python/example/hello/greet/greet 4 0 0 0 100%
------------------------------------------------------------------------------------
TOTAL 4 0 0 0 100%
</pre></div>
<h3 id="interactive-debugging-on-test-failure">Interactive Debugging on Test Failure</h3>
<p>You can invoke the Python debugger on a test failure by leaving out the
<code>test</code> and passing <code>--pdb</code>. This can be useful for inspecting the
state of objects especially if you are mocking interfaces.</p>
<h2 id="building-a-setuppy-distutils-package">Building a <code>setup.py</code> Distutils Package</h2>
<p>You can build Distutils packages from <code>python_library</code> targets.</p>
<p>To make a <code>python_library</code> "setup-able", give it a <code>provides</code> parameter; this parameter's value
should be a <a href="build_dictionary.html#bdict_setup_py" pantsref="bdict_setup_py"><code>setup_py</code></a> call; this call's parameters will be
passed to the <code>setup</code> function.</p>
<div class="codehilite"><pre><span class="n">python_library</span><span class="p">(</span>
<span class="n">name</span><span class="o">=</span><span class="s">'test_infra'</span><span class="p">,</span>
<span class="n">dependencies</span><span class="o">=</span><span class="p">[</span>
<span class="s">'tests/python/pants_test:base_test'</span><span class="p">,</span>
<span class="o">...</span>
<span class="p">],</span>
<span class="n">provides</span><span class="o">=</span><span class="n">setup_py</span><span class="p">(</span>
<span class="n">name</span><span class="o">=</span><span class="s">'pantsbuild.pants.testinfra'</span><span class="p">,</span>
<span class="n">version</span><span class="o">=</span><span class="s">'0.0.24'</span><span class="p">,</span>
<span class="n">description</span><span class="o">=</span><span class="s">'Test support for writing pants plugins.'</span><span class="p">,</span>
<span class="n">long_description</span><span class="o">=</span><span class="s">'''A much longer description of this package. Pages and pages!'''</span><span class="p">,</span>
<span class="n">url</span><span class="o">=</span><span class="s">'https://github.com/pantsbuild/pants'</span><span class="p">,</span>
<span class="n">license</span><span class="o">=</span><span class="s">'Apache License, Version 2.0'</span><span class="p">,</span>
<span class="n">zip_safe</span><span class="o">=</span><span class="bp">True</span><span class="p">,</span>
<span class="n">namespace_packages</span><span class="o">=</span><span class="p">[</span><span class="s">'pants_test'</span><span class="p">],</span>
<span class="n">classifiers</span><span class="o">=</span><span class="p">[</span>
<span class="s">'Intended Audience :: Developers'</span><span class="p">,</span>
<span class="s">'License :: OSI Approved :: Apache Software License'</span><span class="p">,</span>
<span class="s">'Operating System :: MacOS :: MacOS X'</span><span class="p">,</span>
<span class="s">'Operating System :: POSIX :: Linux'</span><span class="p">,</span>
<span class="s">'Programming Language :: Python'</span><span class="p">,</span>
<span class="s">'Topic :: Software Development :: Build Tools'</span><span class="p">,</span>
<span class="s">'Topic :: Software Development :: Testing'</span><span class="p">,</span>
<span class="p">]</span>
<span class="p">)</span>
<span class="p">)</span>
</pre></div>
<p>The <a href="options_reference.html#oref_goal_setup-py" pantsref="oref_goal_setup-py"><code>setup-py</code></a> goal builds a package from such a target:</p>
<div class="codehilite"><pre><span class="nv">$ </span>./pants setup-py src/python/pants:test_infra
10:23:06 00:00 <span class="o">[</span>main<span class="o">]</span>
<span class="o">(</span>To run a reporting server: ./pants server<span class="o">)</span>
10:23:07 00:01 <span class="o">[</span>bootstrap<span class="o">]</span>
10:23:07 00:01 <span class="o">[</span>setup<span class="o">]</span>
10:23:07 00:01 <span class="o">[</span>parse<span class="o">]</span>
Executing tasks in goals: setup-py
10:23:07 00:01 <span class="o">[</span>setup-py<span class="o">]</span>
10:23:07 00:01 <span class="o">[</span>setup-py<span class="o">]</span>
Running packager against /Users/you/workspace/pants/dist/pantsbuild.pants.testinfra-0.0.24
Writing /Users/you/workspace/pants/dist/pantsbuild.pants.testinfra-0.0.24.tar.gz
SUCCESS
</pre></div>
<h2 id="manipulating-pex-behavior-with-environment-variables">Manipulating PEX behavior with environment variables</h2>
<p>You can alter a PEX file's behavior during invocation by setting some
environment variables.</p>
<h3 id="pex_interpreter1"><code>PEX_INTERPRETER=1</code></h3>
<p>If you have a PEX file with a prescribed executable source or
<code>entry_point</code>, you can still drop into an interpreter with the
environment bootstrapped. Set <code>PEX_INTERPRETER=1</code> in your environment,
and the PEX bootstrapper skips any execution and instead launches an
interactive interpreter session.</p>
<h3 id="pex_verbose1"><code>PEX_VERBOSE=1</code></h3>
<p>If your environment is failing to bootstrap or simply bootstrapping very
slowly, it can be useful to set <code>PEX_VERBOSE=1</code> in your environment to
get debugging output printed to the console. Debugging output includes:</p>
<ol>
<li>Fetched dependencies</li>
<li>Built dependencies</li>
<li>Activated dependencies</li>
<li>Packages scrubbed out of sys.path</li>
<li>The sys.path used to launch the interpreter</li>
</ol>
<h3 id="pex_moduleentry_point"><code>PEX_MODULE=entry_point</code></h3>
<p>If you have a PEX file without a prescribed entry point, or want to
change the <code>entry_point</code> for a single invocation, you can set
<code>PEX_MODULE=entry_point</code> using the same format as described in the
<a href="build_dictionary.html#bdict_python_binary" pantsref="bdict_python_binary"><code>python_binary</code></a> Pants target.</p>
<p>This can be useful for bundling up some packages together and using that
single file to execute scripts from each of them.</p>
<p>Another common pattern is to link pytest into your PEX file, and run
<code>PEX_MODULE=pytest my_pex.pex tests/*.py</code> to run your test suite in its
isolated environment.</p>
<h3 id="pex_coverage"><code>PEX_COVERAGE</code></h3>
<p>There is nascent support for performing code coverage within PEX files
by setting <code>PEX_COVERAGE=<suffix></code>. By default the coverage files will
be written into the current working directory with the file pattern
<code>.coverage.<suffix></code>. This requires that the coverage Python module has
been linked into your PEX.</p>
<p>You can then combine the coverage files by running <code>PEX_MODULE=coverage</code>
<code>my_pex.pex</code> <code>.coverage.suffix*</code> and run a report using
<code>PEX_MODULE=coverage</code>
<code>my_pex.pex</code> report. Since PEX files are just zip files, coverage is able
to understand and extract source and line numbers from them in order to
produce coverage reports.</p>
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