The error is raised because pytest captures output by default.

You can run pytest with `-s` option (turn off capture output). For example:

    py.test -s my_test.py

and then in `my_test.py`:

    import ipdb;
    ipdb.set_trace()



pytest-ipdb is unfortunately not supported anymore.

The solution is to run 
`pytest my_test.py --pdb --pdbcls=IPython.terminal.debugger:Pdb`

From the help command:

    pytest -h
      --pdb                 start the interactive Python debugger on errors.
      --pdbcls=modulename:classname
                            start a custom interactive Python debugger on errors.
                            For example:
                            --pdbcls=IPython.terminal.debugger:TerminalPdb


The difference is just that TerminalPdb seems to throw erros, but Pdb not ([Ipython docs][1]). 


  [1]: https://ipython.readthedocs.io/en/latest/api/generated/IPython.core.debugger.html#IPython.core.debugger.Pdb

As of **2019-11** here is what should fix it:
```
pip install ipdb gnureadline ptpython

export PYTEST_ADDOPTS=&#39;--pdb --pdbcls=IPython.terminal.debugger:Pdb&#39;
```


This is what I use

```py.test tests/ --pdbcls=IPython.core.debugger:Pdb -s```

You may want to give `pdbpp` a try.  I&#39;ve had more success with it, compared to `ipdb` when used with `pytest`.  See my answer here: https://stackoverflow.com/a/69320311/2896799.

Im creating a Login using a `window control` to allow a user to login into a `WPF` application that I am creating. 

So far, I have created a method that checks whether the user has entered in the correct credentials for the `username` and `password` in a `textbox` on the login screen, `binding` two `properties`. 

I have achieved this by creating a `bool` method, like so;

    public bool CheckLogin()
    {
        var user = context.Users.Where(i =&gt; i.Username == this.Username).SingleOrDefault();

        if (user == null)
        {
            MessageBox.Show(&quot;Unable to Login, incorrect credentials.&quot;);
            return false;
        }
        else if (this.Username == user.Username || this.Password.ToString() == user.Password)
        {
            MessageBox.Show(&quot;Welcome &quot; + user.Username + &quot;, you have successfully logged in.&quot;);

            return true;
        }
        else
        {
            MessageBox.Show(&quot;Unable to Login, incorrect credentials.&quot;);
            return false;
        }
    }

    public ICommand ShowLoginCommand
    {
        get
        {
            if (this.showLoginCommand == null)
            {
                this.showLoginCommand = new RelayCommand(this.LoginExecute, null);
            }
            return this.showLoginCommand;
        }
    }

    private void LoginExecute()
    {
        this.CheckLogin();
    } 

I also have a `command` that I `bind` to my button within the `xaml` like so;

    &lt;Button Name=&quot;btnLogin&quot; IsDefault=&quot;True&quot; Content=&quot;Login&quot; Command=&quot;{Binding ShowLoginCommand}&quot; /&gt;

When I enter in the username and password it executes the appropriated code, whether it being right, or wrong. But how can I close this window from the ViewModel when both username and password are correct?

I have previously tried using a `dialog modal` but it didn&#39;t quite work out. Furthermore, within my app.xaml, I have done something like the following, which loads the login page first, then once true, loads the actual application.

    private void ApplicationStart(object sender, StartupEventArgs e)
    {
        Current.ShutdownMode = ShutdownMode.OnExplicitShutdown;

        var dialog = new UserView();

        if (dialog.ShowDialog() == true)
        {
            var mainWindow = new MainWindow();
            Current.ShutdownMode = ShutdownMode.OnMainWindowClose;
            Current.MainWindow = mainWindow;
            mainWindow.Show();
        }
        else
        {
            MessageBox.Show(&quot;Unable to load application.&quot;, &quot;Error&quot;, MessageBoxButton.OK);
            Current.Shutdown(-1);
        }
    }

**Question: How can I close the Login `Window control` from the ViewModel?**

Thanks in advance.

Close Window from ViewModel

I want to convert my ipython-notebooks to print them, or simply send them in html format. I have noticed that there exists a tool to do that already, [nbconvert][1]. Although I have downloaded it, I have no idea how to convert the notebook, with nbconvert2.py since nbconvert says that it is deprecated. nbconvert2.py says that I need a profile to convert the notebook, what is it? Does there exist a documentation about this tool?

  [1]: https://github.com/ipython/nbconvert

How to convert IPython notebooks to PDF and HTML?

I&#39;m using pytest for my test suite. While catching bugs in complex inter-components test, I would like to place ``import ipdb; ipdb.set_trace()`` in the middle of my code to allow me to debug it.

However, since pytest traps sys.stdin/sys.stdout ipdb fails. How can I use ipdb while testing with pytest.

I&#39;m not interested in jumping to pdb or ipdb after a failure, but to place breaks anywhere in the code and be able to debug it there before the failure occurs.

How to execute ipdb.set_trace() at will while running pytest tests

I'm using pytest for my test suite. While catching bugs in complex inter-components test, I would like to place <code>import ipdb; ipdb.set_trace()</code> in the middle of my code to allow me to debug it.
However, since pytest traps sys.stdin/sys.stdout ipdb fails. How can I use ipdb while testing with pytest.
I'm not interested in jumping to pdb or ipdb after a failure, but to place breaks anywhere in the code and be able to debug it there before the failure occurs.

Should I make several docstrings, or just one (and where should I put it)?

    @property
    def x(self):
         return 0
    @x.setter
    def x(self, values):
         pass

I see that `property()` accepts a doc argument.

What is the right way to put a docstring on Python property?

I&#39;ve got a Pandas DataFrame and I want to combine the &#39;lat&#39; and &#39;long&#39; columns to form a tuple.

    &lt;class &#39;pandas.core.frame.DataFrame&#39;&gt;
    Int64Index: 205482 entries, 0 to 209018
    Data columns:
    Month           205482  non-null values
    Reported by     205482  non-null values
    Falls within    205482  non-null values
    Easting         205482  non-null values
    Northing        205482  non-null values
    Location        205482  non-null values
    Crime type      205482  non-null values
    long            205482  non-null values
    lat             205482  non-null values
    dtypes: float64(4), object(5)

The code I tried to use was:

    def merge_two_cols(series): 
        return (series[&#39;lat&#39;], series[&#39;long&#39;])
    
    sample[&#39;lat_long&#39;] = sample.apply(merge_two_cols, axis=1)

However, this returned the following error:

    ---------------------------------------------------------------------------
     AssertionError                            Traceback (most recent call last)
    &lt;ipython-input-261-e752e52a96e6&gt; in &lt;module&gt;()
          2     return (series[&#39;lat&#39;], series[&#39;long&#39;])
          3 
    ----&gt; 4 sample[&#39;lat_long&#39;] = sample.apply(merge_two_cols, axis=1)
          5

...

    AssertionError: Block shape incompatible with manager 

How can I solve this problem?

How to form tuple column from two columns in Pandas

I don&#39;t understand what does comma after variable **lines,** means: http://matplotlib.org/examples/animation/simple_anim.html

    line, = ax.plot(x, np.sin(x))

If I remove comma and variable &quot;line,&quot; becomes variable &quot;line&quot; then program is broken. Full code from url given above:

    import numpy as np
    import matplotlib.pyplot as plt
    import matplotlib.animation as animation
    
    fig = plt.figure()
    ax = fig.add_subplot(111)
    
    x = np.arange(0, 2*np.pi, 0.01)        # x-array
    line, = ax.plot(x, np.sin(x))
    
    def animate(i):
        line.set_ydata(np.sin(x+i/10.0))  # update the data
        return line,
    
    #Init only required for blitting to give a clean slate.
    def init():
        line.set_ydata(np.ma.array(x, mask=True))
        return line,
    
    ani = animation.FuncAnimation(fig, animate, np.arange(1, 200), init_func=init,
        interval=25, blit=True)
    plt.show()

According to http://docs.python.org/3/tutorial/datastructures.html#tuples-and-sequences comma after variable seems to be related to tuples containing only one item.

x, = ... - is this trailing comma the comma operator?

I just found out about the configuration option `CELERYD_PREFETCH_MULTIPLIER` ([docs](http://docs.celeryproject.org/en/latest/configuration.html#std:setting-CELERYD_PREFETCH_MULTIPLIER)). The default is 4, but (I believe) I want the prefetching off or as low as possible. I set it to 1 now, which is close enough to what I&#39;m looking for, but there&#39;s still some things I don&#39;t understand:

 1. Why is this prefetching a good idea? I don&#39;t really see a reason for it, unless there&#39;s a lot of latency between the message queue and the workers (in my case, they are currently running on the same host and at worst might eventually run on different hosts in the same data center). The documentation only mentions the disadvantages, but fails to explain what the advantages are.

 2. Many people seem to set this to 0, expecting to be able to turn off prefetching that way (a reasonable assumption in my opinion). However, 0 means unlimited prefetching. Why would anyone ever want unlimited prefetching, doesn&#39;t that entirely eliminate the concurrency/asynchronicity you introduced a task queue for in the first place?

 3. Why can prefetching not be turned off? It might not be a good idea for performance to turn it off in most cases, but is there a technical reason for this not to be possible? Or is it just not implemented?

 4. Sometimes, this option is connected to `CELERY_ACKS_LATE`. For example. [Roger Hu writes](http://hustoknow.blogspot.com/2011/08/what-prefetch-in-celery-means.html#reserve-one-task-at-a-time) &#171;[…] often what [users] really want is to have a worker only reserve as many tasks as there are child processes. But this is not possible without enabling late acknowledgements […]&#187; I don&#39;t understand how these two options are connected and why one is not possible without the other. Another mention of the connection can be found [here](https://groups.google.com/forum/?fromgroups=#!topic/celery-users/q-PYCoKJEz4). Can someone explain why the two options are connected?

Understanding celery task prefetching

I&#39;ve spent the past few hours reading around in here and elsewhere, as well as experimenting, but I&#39;m not really understanding what I am sure is a very basic concept: passing values (as variables) between different functions. 

For example, I assign a whole bunch of values to a list in one function, then want to use that list in another function later:

    list = []

    def defineAList():
        list = [&#39;1&#39;,&#39;2&#39;,&#39;3&#39;]
        print &quot;For checking purposes: in defineAList, list is&quot;,list
        return list

    def useTheList(list):
        print &quot;For checking purposes: in useTheList, list is&quot;,list

    def main():
        defineAList()
        useTheList(list)

    main()

Based on my understanding of what function arguments do, I would expect this to do as follows:

1. Initialize &#39;list&#39; as an empty list; call main (this, at least, I know I&#39;ve got right...)
2. Within defineAList(), assign certain values into the list; then pass the new list back into main() 
3. Within main(), call useTheList(list)
4. Since &#39;list&#39; is included in the parameters of the useTheList function, I would expect that useTheList would now use the list as defined by defineAList(), NOT the empty list defined before calling main.

However, this is obviously a faulty understanding. My output is:
    
    For checking purposes: in defineAList, list is [&#39;1&#39;, &#39;2&#39;, &#39;3&#39;]
    For checking purposes: in useTheList, list is []

So, since &quot;return&quot; obviously does not do what I think it does, or at least it does not do it the way I think it should... what does it actually do? Could you please show me, using this example, what I would have to do to take the list from defineAList() and use it within useTheList()? I tend to understand things better when I see them happening, but a lot of the examples of proper argument-passing I&#39;ve seen also use code I&#39;m not familiar with yet, and in the process of figuring out what&#39;s going on, I&#39;m not really getting a handle on this concept. I&#39;m using 2.7.

ETA- in the past, asking a similar question, it was suggested that I use a global variable instead of just locals. If it will be relevant here also- for the purposes of the class I&#39;m taking, we&#39;re not permitted to use globals. 

Thank you! 

Python: Passing variables between functions

Is there some way to speed up the repeated execution of `pytest`? It seems to spend a lot of time collecting tests, even if I specify which files to execute on the command line. I know it isn&#39;t a disk speed issue either since running pyflakes across all the .py files is very fast.

----

The various answers represent different ways pytest can be slow. They helped sometimes, did not in others. I&#39;m adding one more answer that explains a common speed problem. But it&#39;s not possible to select &quot;The&quot; answer here.

How to speed up pytest

I&#39;m trying to figure out how to get `python setup.py test` to run the equivalent of `python -m unittest discover`.  I don&#39;t want to use a run_tests.py script and I don&#39;t want to use any external test tools (like `nose` or `py.test`).  It&#39;s OK if the solution only works on python 2.7.

In `setup.py`, I think I need to add something to the `test_suite` and/or `test_loader` fields in config, but I can&#39;t seem to find a combination that works correctly:

    config = {
        &#39;name&#39;: name,
        &#39;version&#39;: version,
        &#39;url&#39;: url,
        &#39;test_suite&#39;: &#39;???&#39;,
        &#39;test_loader&#39;: &#39;???&#39;,
    }

**Is this possible using only `unittest` built into python 2.7?**

FYI, my project structure looks like this:

    project/
      package/
        __init__.py
        module.py
      tests/
        __init__.py
        test_module.py
      run_tests.py &lt;- I want to delete this
      setup.py

**Update**: This is possible with `unittest2` but I want find something equivalent using only `unittest`

From https://pypi.python.org/pypi/unittest2

&gt; unittest2 includes a very basic setuptools compatible test collector. Specify test_suite = &#39;unittest2.collector&#39; in your setup.py. This starts test discovery with the default parameters from the directory containing setup.py, so it is perhaps most useful as an example (see unittest2/collector.py).

For now, I&#39;m just using a script called `run_tests.py`, but I&#39;m hoping I can get rid of this by moving to a solution that only uses `python setup.py test`.

Here&#39;s the `run_tests.py` I&#39;m hoping to remove:

    import unittest

    if __name__ == &#39;__main__&#39;:
        
        # use the default shared TestLoader instance
        test_loader = unittest.defaultTestLoader
        
        # use the basic test runner that outputs to sys.stderr
        test_runner = unittest.TextTestRunner()
        
        # automatically discover all tests in the current dir of the form test*.py
        # NOTE: only works for python 2.7 and later
        test_suite = test_loader.discover(&#39;.&#39;)
        
        # run the test suite
        test_runner.run(test_suite)

How to run unittest discover from &quot;python setup.py test&quot;?

I am using pytest. I have two files in a directory. In one of the files there is a long running test case that generates some output. In the other file there is a test case that reads that output. How can I ensure the proper execution order of the two test cases? Is there any alternative other than puting the test cases in the same file in the proper order?

Test case execution order in pytest

I&#39;m writing selenium tests, with a set of classes, each class containing several tests.  Each class currently opens and then closes Firefox, which has two consequences:

- super slow, opening firefox takes longer than running the test in a class...
- crashes, because after firefox has been closed, trying to reopen it really quickly, from selenium, results in an &#39;Error 54&#39;

I could solve the error 54, probably, by adding a sleep, but it would still be super slow.

So, what I&#39;d like to do is reuse the same Firefox instances across *all* test classes.  Which means I need to run a method before all test classes, and another method after all test classes.  So, &#39;setup_class&#39; and &#39;teardown_class&#39; are not sufficient.


How to run a method before all tests in all classes?

I am using py.test to test some DLL code wrapped in a python class MyTester. 
For validating purpose I need to log some test data during the tests and do more processing afterwards. As I have many test_... files I want to reuse the tester object creation (instance of MyTester) for most of my tests.

As the tester object is the one which got the references to the DLL&#39;s variables and functions I need to pass a list of the DLL&#39;s variables to the tester object for each of the test files (variables to be logged are the same for a test_... file).
The content of the list is used to log the specified data.

My idea is to do it somehow like this:
    
    import pytest

    class MyTester():
        def __init__(self, arg = [&quot;var0&quot;, &quot;var1&quot;]):
            self.arg = arg
            # self.use_arg_to_init_logging_part()

        def dothis(self):
            print &quot;this&quot;

        def dothat(self):
            print &quot;that&quot;

    # located in conftest.py (because other test will reuse it)

    @pytest.fixture()
    def tester(request):
        &quot;&quot;&quot; create tester object &quot;&quot;&quot;
        # how to use the list below for arg?
        _tester = MyTester()
        return _tester

    # located in test_...py

    # @pytest.mark.usefixtures(&quot;tester&quot;) 
    class TestIt():

        # def __init__(self):
        #     self.args_for_tester = [&quot;var1&quot;, &quot;var2&quot;]
        #     # how to pass this list to the tester fixture?

        def test_tc1(self, tester):
           tester.dothis()
           assert 0 # for demo purpose

        def test_tc2(self, tester):
           tester.dothat()
           assert 0 # for demo purpose

Is it possible to achieve it like this or is there even a more elegant way?

Usually I could do it for each test method with some kind of setup function (xUnit-style). But I want to gain some kind of reuse. Does anyone know if this is possible with fixtures at all?

I know I can do something like this: (from the docs)
 
    @pytest.fixture(scope=&quot;module&quot;, params=[&quot;merlinux.eu&quot;, &quot;mail.python.org&quot;])

But I need to the parametrization directly in the test module. 
**Is it possible to access the params attribute of the fixture from the test module?**

Content Type	Original Author	Original Content on Stackoverflow
Question	manu	View Question on Stackoverflow
Solution 1 - Python	petRUShka	View Answer on Stackoverflow
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How to execute ipdb.set_trace() at will while running pytest tests

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How to convert IPython notebooks to PDF and HTML?

Close Window from ViewModel

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