Here&#39;s a list of the programs you can install on windows:

http://www.lfd.uci.edu/~gohlke/pythonlibs/

And you&#39;ll need the following dependencies:
Requires numpy, dateutil, pytz, pyparsing, six


You&#39;re probably looking for:

    pip install python-dateutil

I&#39;m completely new to MongoDB &amp; Mongoose and can&#39;t seem to find an answer as to how to handle migrations when a schema changes.

I&#39;m used to running migration SQL scripts that alter table structure and any underlying data that needs to be changed. This typically involves DB downtime.

How is this typically handled within MongoDB/Mongoose? Any gotcha&#39;s that I need to be aware of?

How to properly handle mongoose schema migrations?

Here is a folder, which contains a lot of `.java` files.

How can I git commit this folder?

If I do the following commands

    git add folder_name
    git commit folder_name -m &quot;commit operation&quot;

I will see the messages
nothing added to commit but untracked files present (use &quot;git add&quot; to track)

how to git commit a whole folder?

I have successfully installed matplotlib with python 2.6 on x64 Windows7. When I try to import matplotlib, it shows the following error. I have also installed numpy following this link: https://stackoverflow.com/questions/11200137/installing-numpy-on-64bit-windows-7-with-python-2-7-3

    import matplotlib.pyplot as plt
    
    Traceback (most recent call last):
      File &quot;&lt;pyshell#2&gt;&quot;, line 1, in &lt;module&gt;
        import matplotlib.pyplot as plt
      File &quot;C:\Python26\Lib\site-packages\matplotlib\__init__.py&quot;, line 110, in &lt;module&gt;
        raise ImportError(&quot;matplotlib requires dateutil&quot;)
    ImportError: matplotlib requires dateutil

How can I make it work?

I installed matplotlib-1.3.0.win-amd64-py2.6.exe from &lt;http://matplotlib.org/downloads.html&gt;

ImportError: matplotlib requires dateutil

I have successfully installed matplotlib with python 2.6 on x64 Windows7. When I try to import matplotlib, it shows the following error. I have also installed numpy following this link: <a href="https://stackoverflow.com/questions/11200137/installing-numpy-on-64bit-windows-7-with-python-2-7-3" target="_blank" rel="noopener noreferrer">https://stackoverflow.com/questions/11200137/installing-numpy-on-64bit-windows-7-with-python-2-7-3</a>
<pre><code class="hljs language-java">import matplotlib.pyplot as plt

Traceback (most recent call last):
 File "&#x3C;pyshell#2>", line 1, in &#x3C;module>
 import matplotlib.pyplot as plt
 File "C:\Python26\Lib\site-packages\matplotlib\__init__.py", line 110, in &#x3C;module>
 raise ImportError("matplotlib requires dateutil")
ImportError: matplotlib requires dateutil
</code></pre>
How can I make it work?
I installed matplotlib-1.3.0.win-amd64-py2.6.exe from &#x3C;<a href="http://matplotlib.org/downloads.html" target="_blank" rel="noopener noreferrer">http://matplotlib.org/downloads.html</a>>

I have a huge file that I am writing into approximately 450 files. I am getting error as `too many files open`. I searched the web and found some solution but it is not helping. 

    import resource
    resource.setrlimit(resource.RLIMIT_NOFILE, (1000,-1))
    &gt;&gt;&gt; len(pureResponseNames) #Filenames 
    434
    &gt;&gt;&gt; resource.getrlimit(resource.RLIMIT_NOFILE)
    (1000, 9223372036854775807)
    &gt;&gt;&gt; output_files = [open(os.path.join(outpathDirTest, fname) + &quot;.txt&quot;, &quot;w&quot;) for fname in pureResponseNames]
    Traceback (most recent call last):
      File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
    IOError: [Errno 24] Too many open files: &#39;icd9_737.txt&#39;
    &gt;&gt;&gt; 


I also changed `ulimit` from the command line as below:

    $ ulimit -n 1200
    $ ulimit -a
    core file size          (blocks, -c) 0
    data seg size           (kbytes, -d) unlimited
    file size               (blocks, -f) unlimited
    max locked memory       (kbytes, -l) unlimited
    max memory size         (kbytes, -m) unlimited
    open files                      (-n) 1200
    pipe size            (512 bytes, -p) 1
    stack size              (kbytes, -s) 8192
    cpu time               (seconds, -t) unlimited
    max user processes              (-u) 709
    virtual memory          (kbytes, -v) unlimited
    $ 


I am still getting the same error. 
PS: I also restarted my system and run the program but with no success. 



IOError: [Errno 24] Too many open files:

I am concerned about the order of files and directories given by `os.walk()`. If I have these directories, `1`, `10`, `11`, `12`, `2`, `20`, `21`, `22`, `3`, `30`, `31`, `32`, what is the order of the output list?

Is it sorted by numeric values?

    1 2 3 10 20 30 11 21 31 12 22 32

Or sorted by ASCII values, like what is given by `ls`?

    1 10 11 12 2 20 21 22 3 30 31 32

Additionally, how can I get a specific sort?

In what order does os.walk iterates iterate?

I am trying to create a python dictionary which is to be used as a java script var inside a html file for visualization purposes. As a requisite, I am in need of creating the dictionary with all names inside double quotes instead of default single quotes which Python uses. Is there an easy and elegant way to achieve this. 

   

        couples = [
                   [&#39;jack&#39;, &#39;ilena&#39;], 
                   [&#39;arun&#39;, &#39;maya&#39;], 
                   [&#39;hari&#39;, &#39;aradhana&#39;], 
                   [&#39;bill&#39;, &#39;samantha&#39;]]
        pairs = dict(couples)
        print pairs

**Generated Output:**

    {&#39;arun&#39;: &#39;maya&#39;, &#39;bill&#39;: &#39;samantha&#39;, &#39;jack&#39;: &#39;ilena&#39;, &#39;hari&#39;: &#39;aradhana&#39;}

**Expected Output:**

    {&quot;arun&quot;: &quot;maya&quot;, &quot;bill&quot;: &quot;samantha&quot;, &quot;jack&quot;: &quot;ilena&quot;, &quot;hari&quot;: &quot;aradhana&quot;}

I know, `json.dumps(pairs)` does the job, but the dictionary as a whole is converted into a string which isn&#39;t what I am expecting.

**P.S.:** Is there an alternate way to do this with using json, since I am dealing with nested dictionaries.

How to create a Python dictionary with double quotes as default quote format?

When I meet the situation I can do it in javascript, I always think if there&#39;s an `foreach` function it would be convenience. By foreach I mean the function which is described below:

    def foreach(fn,iterable):
        for x in iterable:
            fn(x)

they just do it on every element and didn&#39;t yield or return something,i think it should be a built-in function and should be more faster than writing it with pure Python, but I didn&#39;t found it on the list,or it just called another name?or I just miss some points here?

Maybe I got wrong, cause calling an function in Python cost high, definitely not a good practice for the example. Rather than an out loop, the function should do the loop in side its body looks like this below which already mentioned in many python&#39;s code suggestions:

    def fn(*args):
        for x in args:
           dosomething

but I thought foreach is still welcome base on the two facts:

1. In normal cases, people just don&#39;t care about the performance
2. Sometime the API didn&#39;t accept iterable object and you can&#39;t rewrite its source.

Is there a &#39;foreach&#39; function in Python 3?

I come from OOP background and trying to learn python.
I am using the `max` function which uses a lambda expression to return the instance of type `Player` having maximum `totalScore` among the list `players`.

    def winner():
        w = max(players, key=lambda p: p.totalScore)

The function correctly returns instance of type `Player` having maximum `totalScore`.
I am confused about the following three things:

 1. How does the `max` function work? What are the arguments it is taking? I looked at the documentation but failed to understand.
 2. What is use of the keyword `key` in max function? I know it is also used in context of `sort` function
 3. Meaning of the lambda expression? How to read them? How do they work?


These are all very noobish conceptual questions but will help me understand the language. It would help if you could give examples to explain.
Thanks



python max function using &#39;key&#39; and lambda expression

I&#39;d like to create a stacked histogram.  If I have a single 2-D array, made of three equal length data sets, this is simple.  Code and image below:

    import numpy as np
    from matplotlib import pyplot as plt

    # create 3 data sets with 1,000 samples
    mu, sigma = 200, 25
    x = mu + sigma*np.random.randn(1000,3)

    #Stack the data
    plt.figure()
    n, bins, patches = plt.hist(x, 30, stacked=True, density = True)
    plt.show()

![enter image description here][1]


However, if I try similar code with three data sets of a different length the results are that one histogram covers up another.  Is there any way I can do the stacked histogram with mixed length data sets?

    ##Continued from above
    ###Now as three separate arrays
    x1 = mu + sigma*np.random.randn(990,1)
    x2 = mu + sigma*np.random.randn(980,1)
    x3 = mu + sigma*np.random.randn(1000,1)

    #Stack the data
    plt.figure()
    plt.hist(x1, bins, stacked=True, density = True)
    plt.hist(x2, bins, stacked=True, density = True)
    plt.hist(x3, bins, stacked=True, density = True)
    plt.show()

![enter image description here][2]


  [1]: http://i.stack.imgur.com/4aBSy.png
  [2]: http://i.stack.imgur.com/sZ92m.png

Create stacked histogram from unequal length arrays

I have the following data set.  I would like to use Python or Gnuplot to plot the data.  The tuples are of the form `(x, y)`.  The Y-axis should be a log axis, that is, `log(y)`.  A scatter plot or line plot would be ideal.

How can this be done?

     [(0, 6.0705199999997801e-08), (1, 2.1015700100300739e-08), 
     (2, 7.6280656623374823e-09), (3, 5.7348209304555086e-09), 
     (4, 3.6812203579604238e-09), (5, 4.1572516753310418e-09)]



How do I plot list of tuples in Python?

I have just read a wav file with scipy and now I want to make the plot of the file using matplotlib, on the &quot;y scale&quot; I want to see the aplitude and over the &quot;x scale&quot; I want to see the numbers of frames! 
Any help how can I do this??
Thank you!

    from scipy.io.wavfile import read
    import numpy as np
    from numpy import*
    import matplotlib.pyplot as plt
    a=read(&quot;C:/Users/Martinez/Desktop/impulso.wav&quot;)
    print a

How to plot a wav file

Say I have some input data:

    data = np.random.normal(loc=100,scale=10,size=(500,1,32))
    hist = np.ones((32,20)) # initialise hist
    for z in range(32):
	    hist[z],edges = np.histogram(data[:,0,z],bins=np.arange(80,122,2))

I can plot it using `imshow()`:

    plt.imshow(hist,cmap=&#39;Reds&#39;)

getting: 

![enter image description here][1]

However, the x-axis values do not match the input data (i.e. mean of 100, range from 80 to 122). Therefore, I&#39;d like to change the x-axis to show the values in `edges`.

I have tried:

    ax = plt.gca()
    ax.set_xlabel([80,122]) # range of values in edges
    ...
    # this shifts the plot so that nothing is visible

and 

    ax.set_xticklabels(edges)
    ...
    # this labels the axis but does not centre around the mean:

![enter image description here][2]


Any ideas on how I can change the axis values to reflect the input data I am using?


  [1]: http://i.stack.imgur.com/S8LQF.png
  [2]: http://i.stack.imgur.com/pWeOf.png

Change values on matplotlib imshow() graph axis

How can I prevent a specific plot to be shown in Jupyter notebook? I have several plots in a notebook but I want a subset of them to be saved to a file and not shown on the notebook as this slows considerably.

A minimal working example for a Jupyter notebook is:

    %matplotlib inline 
    from numpy.random import randn
    from matplotlib.pyplot import plot, figure
    a=randn(3)
    b=randn(3)
    for i in range(10):
        fig=figure()
        plot(b)
        fname=&#39;s%03d.png&#39;%i
        fig.savefig(fname)
        if(i%5==0):
            figure()
            plot(a)

As you can see I have two types of plots, a and b. I want a&#39;s to be plotted and shown and I don&#39;t want the b plots to be shown, I just want them them to be saved in a file. Hopefully this will speed things a bit and won&#39;t pollute my notebook with figures I don&#39;t need to see.

Thank you for your time

prevent plot from showing in jupyter notebook

At some point in the last few days, Matplotlib stopped working for me on OS X. Here&#39;s the error I get when trying to `import matplotlib`:

    Traceback (most recent call last):
      File &quot;/my/path/to/script/my_script.py&quot;, line 15, in &lt;module&gt;
        import matplotlib.pyplot as plt
      File &quot;/Library/Python/2.7/site-packages/matplotlib/pyplot.py&quot;, line 34, in &lt;module&gt;
        from matplotlib.figure import Figure, figaspect
      File &quot;/Library/Python/2.7/site-packages/matplotlib/figure.py&quot;, line 40, in &lt;module&gt;
        from matplotlib.axes import Axes, SubplotBase, subplot_class_factory
      File &quot;/Library/Python/2.7/site-packages/matplotlib/axes/__init__.py&quot;, line 4, in &lt;module&gt;
        from ._subplots import *
      File &quot;/Library/Python/2.7/site-packages/matplotlib/axes/_subplots.py&quot;, line 10, in &lt;module&gt;
        from matplotlib.axes._axes import Axes
      File &quot;/Library/Python/2.7/site-packages/matplotlib/axes/_axes.py&quot;, line 22, in &lt;module&gt;
        import matplotlib.dates as _  # &lt;-registers a date unit converter
      File &quot;/Library/Python/2.7/site-packages/matplotlib/dates.py&quot;, line 126, in &lt;module&gt;
        from dateutil.rrule import (rrule, MO, TU, WE, TH, FR, SA, SU, YEARLY,
      File &quot;/Library/Python/2.7/site-packages/dateutil/rrule.py&quot;, line 14, in &lt;module&gt;
        from six.moves import _thread
    ImportError: cannot import name _thread

The only system change I can think of was the Apple-forced NTP update and maybe some permission changes I did in /usr/local to get Brew working again.

I tried reinstalling both Matplotlib and Python-dateutil via Pip, but this did not help.  Also tried a reboot.  I&#39;m running Python 2.7.6, which is located in /usr/bin/python.  I&#39;m running Yosemite (OS X 10.10.1).

Content Type	Original Author	Original Content on Stackoverflow
Question	user2690469	View Question on Stackoverflow
Solution 1 - Python	takrliu	View Answer on Stackoverflow
Solution 2 - Python	David Wolever	View Answer on Stackoverflow

ImportError: matplotlib requires dateutil

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

how to git commit a whole folder?

How to properly handle mongoose schema migrations?

Attributions