Using [`datetime.timedelta`](https://docs.python.org/2/library/datetime.html#datetime.timedelta)

    &gt;&gt;&gt; import datetime
    &gt;&gt;&gt; s = &#39;04/21/2013&#39;
    &gt;&gt;&gt; d = datetime.datetime.strptime(s, &#39;%m/%d/%Y&#39;) + datetime.timedelta(days=1)
    &gt;&gt;&gt; print(d.strftime(&#39;%m/%d/%Y&#39;))
    04/22/2013

Same answer as a one-liner. Prints 1 day 1 hour &amp; 30 minutes ago from now:

    python -c &#39;import datetime;print(datetime.datetime.now() - datetime.timedelta(days=1,hours=1,minutes=30))&#39;

    2022-02-08 13:11:06.304608


I have following jQuery code to prevent double clicking a button. It works fine. I am using `Page_ClientValidate()` to ensure that the double click is prevented only if the page is valid.  [If there are validation errors the flag should not be set as there is no postback to server started]

Is there a better method to prevent the second click on the button before the page loads back? 

Can we set the flag  `isOperationInProgress = yesIndicator` only if the page is causing a postback to server? Is there a suitable `event` for it that will be called before the user can click on the button for the second time?

**Note**: I am looking for a solution that won&#39;t require any new API

**Note**: This question is not a duplicate. Here I am trying to avoid the use of `Page_ClientValidate()`. Also I am looking for an `event` where I can move the code so that I need not use `Page_ClientValidate()` 

**Note**: No ajax involved in my scenario. The `ASP.Net` form will be submitted to server synchronously. The button click event in javascript is only for preventing double click. The form submission is synchronous using ASP.Net.

**Present Code**  
 
    $(document).ready(function () {
      var noIndicator = &#39;No&#39;;
      var yesIndicator = &#39;Yes&#39;;
      var isOperationInProgress = &#39;No&#39;;
 
      $(&#39;.applicationButton&#39;).click(function (e) {
        // Prevent button from double click
        var isPageValid = Page_ClientValidate();
        if (isPageValid) {
          if (isOperationInProgress == noIndicator) {
            isOperationInProgress = yesIndicator;
          } else {
            e.preventDefault();
          }
        } 
      });
    });

**References**:

1. https://stackoverflow.com/questions/13825543/validator-causes-improper-behavior-for-double-click-check
2. https://stackoverflow.com/questions/13832818/whether-to-use-page-isvalid-or-page-clientvalidate-for-client-side-events

Note by @Peter Ivan in the above references: 
&gt;calling Page_ClientValidate() repeatedly may cause the page to be too obtrusive (multiple alerts etc.).

Preventing multiple clicks on button

I&#39;m trying to define some class methods using another more generic class method as follows:

    class RGB(object):
        def __init__(self, red, blue, green):
            super(RGB, self).__init__()
            self._red = red
            self._blue = blue
            self._green = green
    
        def _color(self, type):
            return getattr(self, type)
    
        red = functools.partial(_color, type=&#39;_red&#39;)
        blue = functools.partial(_color, type=&#39;_blue&#39;)
        green = functools.partial(_color, type=&#39;_green&#39;)

But when i attempt to invoke any of those methods i get:

    rgb = RGB(100, 192, 240)
    print rgb.red()
    TypeError: _color() takes exactly 2 arguments (1 given)

I guess self is not passed to `_color` since `rgb.red(rgb)` works.

functools.partial on class method

I have a date column in csv file say `Date` having dates in this format `04/21/2013` and I have one more column `Next_Day`. In `Next_Day` column I want to populate the date which comes immediately after the date mentioned in date column. For eg. if date column has `04/21/2013` as date then I want `04/22/2013` in Next_Day column. 

We can use `+1` in excel but I don&#39;t know how to perform this in Python.

Please help me in resolving this.

How to perform arithmetic operation on a date in Python?

I have a date column in csv file say <code>Date</code> having dates in this format <code>04/21/2013</code> and I have one more column <code>Next_Day</code>. In <code>Next_Day</code> column I want to populate the date which comes immediately after the date mentioned in date column. For eg. if date column has <code>04/21/2013</code> as date then I want <code>04/22/2013</code> in Next_Day column.
We can use <code>+1</code> in excel but I don't know how to perform this in Python.
Please help me in resolving this.

What is the difference between the `/usr/bin/python3` and `/usr/bin/python3m` executibles?

I am observing them on Ubuntu 13.04, but Google suggests that they exist on other distributions too.

The two files have the same md5sum, but do not seem to be symbolic links or hard links; the two files have different inode numbers returned by `ls -li` and testing `find -xdev -samefile /usr/bin/python3.3` does not return any other files.

Someone asked a [similar question on AskUbuntu][1], but I wanted to find out more about the difference between the two files. 


  [1]: https://askubuntu.com/questions/215925/what-is-python3mu

Difference between python3 and python3m executables

As far as I know, in C &amp; C++, the priority sequence for NOT AND &amp; OR is NOT&gt;AND&gt;OR. But this doesn&#39;t seem to work in a similar way in Python. I tried searching for it in the Python documentation and failed (Guess I&#39;m a little impatient.). Can someone clear this up for me?

Priority of the logical operators NOT, AND, OR in Python

[Requests][1] is a really nice library. I&#39;d like to use it for downloading big files (&gt;1GB).
The problem is it&#39;s not possible to keep whole file in memory; I need to read it in chunks. And this is a problem with the following code:

    import requests

    def DownloadFile(url)
        local_filename = url.split(&#39;/&#39;)[-1]
        r = requests.get(url)
        f = open(local_filename, &#39;wb&#39;)
        for chunk in r.iter_content(chunk_size=512 * 1024): 
            if chunk: # filter out keep-alive new chunks
                f.write(chunk)
        f.close()
        return 

For some reason it doesn&#39;t work this way: it still loads the response into memory before it is saved to a file.


**UPDATE**

If you need a small client (Python 2.x /3.x) which can download big files from FTP, you can find it [here][2]. It supports multithreading &amp; reconnects (it does monitor connections) also it tunes socket params for the download task. 

  [1]: https://requests.readthedocs.io/
  [2]: https://github.com/keepitsimple/pyFTPclient

Download large file in python with requests

Good day! Need to convert xml using xslt in Python. I have a sample code in php. 

How to implement this in Python or where to find something similar? Thank you!

    $xmlFileName = dirname(__FILE__).&quot;example.fb2&quot;;
    $xml = new DOMDocument();
    $xml-&gt;load($xmlFileName);

    $xslFileName = dirname(__FILE__).&quot;example.xsl&quot;;
    $xsl = new DOMDocument;
    $xsl-&gt;load($xslFileName);

    // Configure the transformer
    $proc = new XSLTProcessor();
    $proc-&gt;importStyleSheet($xsl); // attach the xsl rules
    echo $proc-&gt;transformToXML($xml);

How to transform an XML file using XSLT in Python?

My application: I am trying to rotate an image (using OpenCV and Python)

![Rotating Images][1]

At the moment I have developed the below code which rotates an input image, padding it with black borders, giving me A. What I want is B - the largest possible area crop window within the rotated image. I call this the axis-aligned boundED box.

This is essentially the same as https://stackoverflow.com/questions/16255037/rotate-and-crop, however I cannot get the answer on that question to work. Additionally, that answer is apparently only valid for square images. My images are rectangular.

Code to give A:


    import cv2
    import numpy as np
    
    
    def getTranslationMatrix2d(dx, dy):
        &quot;&quot;&quot;
        Returns a numpy affine transformation matrix for a 2D translation of
        (dx, dy)
        &quot;&quot;&quot;
        return np.matrix([[1, 0, dx], [0, 1, dy], [0, 0, 1]])
    
    
    def rotateImage(image, angle):
        &quot;&quot;&quot;
        Rotates the given image about it&#39;s centre
        &quot;&quot;&quot;
        
        image_size = (image.shape[1], image.shape[0])
        image_center = tuple(np.array(image_size) / 2)
    
        rot_mat = np.vstack([cv2.getRotationMatrix2D(image_center, angle, 1.0), [0, 0, 1]])
        trans_mat = np.identity(3)
    
        w2 = image_size[0] * 0.5
        h2 = image_size[1] * 0.5
    
        rot_mat_notranslate = np.matrix(rot_mat[0:2, 0:2])
        
        tl = (np.array([-w2, h2]) * rot_mat_notranslate).A[0]
        tr = (np.array([w2, h2]) * rot_mat_notranslate).A[0]
        bl = (np.array([-w2, -h2]) * rot_mat_notranslate).A[0]
        br = (np.array([w2, -h2]) * rot_mat_notranslate).A[0]
    
        x_coords = [pt[0] for pt in [tl, tr, bl, br]]
        x_pos = [x for x in x_coords if x &gt; 0]
        x_neg = [x for x in x_coords if x &lt; 0]
    
        y_coords = [pt[1] for pt in [tl, tr, bl, br]]
        y_pos = [y for y in y_coords if y &gt; 0]
        y_neg = [y for y in y_coords if y &lt; 0]
    
        right_bound = max(x_pos)
        left_bound = min(x_neg)
        top_bound = max(y_pos)
        bot_bound = min(y_neg)
    
        new_w = int(abs(right_bound - left_bound))
        new_h = int(abs(top_bound - bot_bound))
        new_image_size = (new_w, new_h)
    
        new_midx = new_w * 0.5
        new_midy = new_h * 0.5
    
        dx = int(new_midx - w2)
        dy = int(new_midy - h2)
    
        trans_mat = getTranslationMatrix2d(dx, dy)
        affine_mat = (np.matrix(trans_mat) * np.matrix(rot_mat))[0:2, :]
        result = cv2.warpAffine(image, affine_mat, new_image_size, flags=cv2.INTER_LINEAR)
    
        return result

  [1]: http://i.stack.imgur.com/KWoeo.jpg

Rotate image and crop out black borders

I have a record ``foo`` in the database which has `:start_time` and `:timezone` attributes.

The `:start_time` is a Time in UTC - `2001-01-01 14:20:00`, for example.
The `:timezone` is a string - `America/New_York`, for example.

I want to create a new Time object with the value of `:start_time` but whose timezone is specified by `:timezone`. I do not want to load the `:start_time` and then convert to `:timezone`, because Rails will be clever and update the time from UTC to be consistent with that timezone.

Currently,

    t = foo.start_time
    =&gt; 2000-01-01 14:20:00 UTC
    t.zone
    =&gt; &quot;UTC&quot;
    t.in_time_zone(&quot;America/New_York&quot;)
    =&gt; Sat, 01 Jan 2000 09:20:00 EST -05:00
    
Instead, I want to see

    =&gt; Sat, 01 Jan 2000 14:20:00 EST -05:00
    
ie. I want to do:

    t
    =&gt; 2000-01-01 14:20:00 UTC
    t.zone = &quot;America/New_York&quot;
    =&gt; &quot;America/New_York&quot;
    t
    =&gt; 2000-01-01 14:20:00 EST

Ruby / Rails - Change the timezone of a Time, without changing the value

I have a variable and I need to know if it is a datetime object.

So far I have been using the following hack in the function to detect datetime object:

    if &#39;datetime.datetime&#39; in str(type(variable)):
         print(&#39;yes&#39;)

But there really should be a way to detect what type of object something is. Just like I can do:

    if type(variable) is str: print &#39;yes&#39;

Is there a way to do this other than the hack of turning the name of the object type into a string and seeing if the string contains `&#39;datetime.datetime&#39;`?

Detect if a variable is a datetime object

From what I gather, [here](http://pleac.sourceforge.net/pleac_python/datesandtimes.html) (for example), this should print the current year in two digits

    print (datetime.strftime(&quot;%y&quot;))

However, I get this error 

    TypeError: descriptor &#39;strftime&#39; requires a &#39;datetime.date&#39; object but received a &#39;str&#39;

So I tried to this

    print (datetime.strftime(datetime.date()))

to get 

    TypeError: descriptor &#39;date&#39; of &#39;datetime.datetime&#39; object needs an argument

so I placed ``&quot;%y&quot;`` inside of thr ``date()`` above to get 

    TypeError: descriptor &#39;date&#39; requires a &#39;datetime.datetime&#39; object but received a &#39;str&#39;

Which start to seem really loopy and fishy to me. 

What am I missing? 

How to print current date on python3?

Please what&#39;s wrong with my code: 

    import datetime
    d = &quot;2013-W26&quot;
    r = datetime.datetime.strptime(d, &quot;%Y-W%W&quot;)
    print(r)

Display &quot;2013-01-01 00:00:00&quot;, Thanks.

Get date from week number

I would like to iterate through a range of calender dates, each iteration is +1 day. I would use something built around JodaTime in Java - is there something similar in NodeJS?


Iterate through a range of dates in NodeJS

I&#39;m a bit confused about how/why so many python developers use `if not` in their conditional statements. 

for example, lets say we had a function, 

    def foo(bar = None):
        if not bar:
            bar = 2

But why go about this way? I mean, wouldn&#39;t doing `if bar != None` or `if bar is not None`be more explicit? What does `if not` try to say? 

Python &#39;If not&#39; syntax

I&#39;m coding a REST API with [Django REST framework][1]. The API will be the backend of a social mobile app. After following the tutorial, I can serialise all my models and I am able to create new resources and update them.

I&#39;m using AuthToken for authentication.

My question is:

Once I have the `/users` resource, I want the app user to be able to register. So, is it better to have a separate resource like `/register` or allow anonymous users to POST to `/users` a new resource?

Also, some guidance about permissions would be great.

[1]: http://www.django-rest-framework.org/

How to register users in Django REST framework?

I want to define a class containing `read` and `write` methods, which can be called as follows:

    instance.read
    instance.write
    instance.device.read
    instance.device.write

To not use interlaced classes, my idea was to overwrite the `__getattr__` and `__setattr__` methods and to check, if the given name is `device` to redirect the return to `self`. But I encountered a problem giving infinite recursions. The example code is as follows:

    class MyTest(object):
        def __init__(self, x):
            self.x = x

        def __setattr__(self, name, value):
            if name==&quot;device&quot;:
                print &quot;device test&quot;
            else:
                setattr(self, name, value)

    test = MyTest(1)


As in `__init__` the code tried to create a new attribute `x`, it calls `__setattr__`, which again calls `__setattr__` and so on. How do I need to change this code, that, in this case, a new attribute `x` of `self` is created, holding the value `1`? 

Or is there any better way to handle calls like `instance.device.read` to be &#39;mapped&#39; to `instance.read`? 

As there are always questions about the why: I need to create abstractions of `xmlrpc` calls, for which very easy methods like `myxmlrpc.instance,device.read` and similar can be created. I need to &#39;mock&#39; this up to mimic such multi-dot-method calls.

How to use __setattr__ correctly, avoiding infinite recursion

I am trying to read an excel file this way :
    
    newFile = pd.ExcelFile(PATH\FileName.xlsx)
    ParsedData = pd.io.parsers.ExcelFile.parse(newFile)

which throws an error that says two arguments expected, I don&#39;t know what the second argument is and also what I am trying to achieve here is to convert an Excel file to a DataFrame, Am I doing it the right way? or is there any other way to do this using pandas?



Reading an Excel file in python using pandas

I like to know, which is the best practice to declare dictionary in below 2 approaches and why?

    &gt;&gt;&gt;a=dict(one=2, two=3)  # {&quot;two&quot;:3, &quot;one&quot;:2}
    &gt;&gt;&gt;a={&quot;two&quot;:3, &quot;one&quot;:2}


Content Type	Original Author	Original Content on Stackoverflow
Question	atams	View Question on Stackoverflow
Solution 1 - Python	jamylak	View Answer on Stackoverflow
Solution 2 - Python	Robert Ranjan	View Answer on Stackoverflow

How to perform arithmetic operation on a date in Python?

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

functools.partial on class method

Preventing multiple clicks on button

Attributions