You can use the [`length` filter](http://jinja.pocoo.org/docs/templates/#length):

    {% if some_var|length &gt; 1 %}

I am using bootstrap date-picker in my angular application. However when I select a date from that date-picker underlying ng-model that I have bind gets updated I want that ng-model in one date format &#39;MM/dd/yyyy&#39;. but it every times makes date like this 

    &quot;2009-02-03T18:30:00.000Z&quot;

instead of 

    02/04/2009

I have created a plunkr for the same [plunkr link][1]

My Html and controller code is like below

    &lt;!doctype html&gt;
    &lt;html ng-app=&quot;plunker&quot;&gt;
      &lt;head&gt;
        &lt;script src=&quot;//ajax.googleapis.com/ajax/libs/angularjs/1.2.10/angular.js&quot;&gt;&lt;/script&gt;
        &lt;script src=&quot;//angular-ui.github.io/bootstrap/ui-bootstrap-tpls-0.11.0.js&quot;&gt;&lt;/script&gt;
        &lt;script src=&quot;example.js&quot;&gt;&lt;/script&gt;
        &lt;link href=&quot;//netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css&quot; rel=&quot;stylesheet&quot;&gt;
      &lt;/head&gt;
      &lt;body&gt;
    
    &lt;div ng-controller=&quot;DatepickerDemoCtrl&quot;&gt;
        &lt;pre&gt;Selected date is: &lt;em&gt;{{dt | date:&#39;MM/dd/yyyy&#39; }}&lt;/em&gt;&lt;/pre&gt;
        &lt;p&gt;above filter will just update above UI but I want to update actual ng-modle&lt;/p&gt;
        
    
        &lt;h4&gt;Popup&lt;/h4&gt;
        &lt;div class=&quot;row&quot;&gt;
            &lt;div class=&quot;col-md-6&quot;&gt;
                &lt;p class=&quot;input-group&quot;&gt;
                  &lt;input type=&quot;text&quot; class=&quot;form-control&quot;
                  datepicker-popup=&quot;{{format}}&quot; 
                  ng-model=&quot;dt&quot;
                  is-open=&quot;opened&quot; min-date=&quot;minDate&quot;
                  max-date=&quot;&#39;2015-06-22&#39;&quot; 
                  datepicker-options=&quot;dateOptions&quot; 
                  date-disabled=&quot;disabled(date, mode)&quot; 
                  ng-required=&quot;true&quot; close-text=&quot;Close&quot; /&gt;
                  &lt;span class=&quot;input-group-btn&quot;&gt; 
                    &lt;button type=&quot;button&quot; class=&quot;btn btn-default&quot; ng-click=&quot;open($event)&quot;&gt;
                    &lt;i class=&quot;glyphicon glyphicon-calendar&quot;&gt;&lt;/i&gt;&lt;/button&gt;
                  &lt;/span&gt;
                &lt;/p&gt;
            &lt;/div&gt;
        &lt;/div&gt;
        &lt;!--&lt;div class=&quot;row&quot;&gt;
            &lt;div class=&quot;col-md-6&quot;&gt;
                &lt;label&gt;Format:&lt;/label&gt; &lt;select class=&quot;form-control&quot; ng-model=&quot;format&quot; ng-options=&quot;f for f in formats&quot;&gt;&lt;option&gt;&lt;/option&gt;&lt;/select&gt;
            &lt;/div&gt;
        &lt;/div&gt;--&gt;
    
        &lt;hr /&gt;
        {{dt}}
    &lt;/div&gt;
      &lt;/body&gt;
    &lt;/html&gt;

**Angular controller**

    angular.module(&#39;plunker&#39;, [&#39;ui.bootstrap&#39;]);
    var DatepickerDemoCtrl = function ($scope) {
    
    
      $scope.open = function($event) {
        $event.preventDefault();
        $event.stopPropagation();
    
        $scope.opened = true;
      };
    
      $scope.dateOptions = {
        formatYear: &#39;yy&#39;,
        startingDay: 1
      };
    
     
      $scope.format = &#39;dd-MMMM-yyyy&#39;;
    };
Thanks in advance for review my question.

**UPDATE**

I am calling below method for posting my data and VAR is array of size 900 which contains date-picker variables. 

    public SaveCurrentData(formToSave: tsmodels.ResponseTransferCalculationModelTS) {
    
            var query = this.EntityQuery.from(&#39;SaveFormData&#39;).withParameters({
                $method: &#39;POST&#39;,
                $encoding: &#39;JSON&#39;,
                $data: {
                    VAR: formToSave.VAR,
                    X: formToSave.X,
                    CurrentForm: formToSave.currentForm,
                }
            });
    
            var deferred = this.q.defer();
    
            this.manager.executeQuery(query).then((response) =&gt; {
                deferred.resolve(response);
            }, (error) =&gt; {
                    deferred.reject(error);
                });
    
            return deferred.promise;
        }

  [1]: http://plnkr.co/edit/AtjFPbGggVvLLvz69BvH?p=preview

Angular bootstrap datepicker date format does not format ng-model value

When I read the document I found the following notes:

&gt; When a $sort immediately precedes a $limit in the pipeline, the $sort operation only maintains the top n results as it progresses, where n is the specified limit, and MongoDB only needs to store n items in memory. This optimization still applies when allowDiskUse is true and the n items exceed the aggregation memory limit.

If I&#39;m right about this, it applies only when I use the $sort and $limit together like

    db.coll.aggregate([
        ...,
        {$sort: ...},
        {$limit: limit},
        ...
    ]);
However, I think most of the time we would have

    db.coll.aggregate([
        ...,
        {$sort: ...},
        {$skip: skip},
        {$limit: limit},
        ...
    ]);
**Question 1**: Does it mean the rule above doesn&#39;t apply if I use $skip here?

I ask this question because theoretically MongoDB can still  calculate the top **n** records and  enhance performance by sorting only top **n** records. I didn&#39;t find any document about this though. And if the rule doesn&#39;t apply,

**Question 2**: Do I need to change my query to the following to enhance performance?

    db.coll.aggregate([
        ...,
        {$sort: ...},
        {$limit: skip + limit},
        {$skip: skip},
        {$limit: limit},
        ...
    ]);

**EDIT**: I think explains my use case would make the question above makes more sense. I&#39;m using the text search feature provided by MongoDB 2.6 to look for products. I&#39;m worried if the user inputs a very common key word like &quot;red&quot;, there will be too many results returned. Thus I&#39;m looking for better ways to generate this result.

**EDIT2**: It turns out that the last code above equals to 

    db.coll.aggregate([
        ...,
        {$sort: ...},
        {$limit: skip + limit},
        {$skip: skip},
        ...
    ]);
Thus I we can always use this form to make the **top n** rule apply.

$skip and $limit in aggregation framework

Jinja unfortunately does not support executing arbitrary Python code, such as

    {% if len(some_var)&gt;1 %} ... {% endif %}

My current workaround is to use the deprecated, ugly, double-underscore method:

    {% if some_var.__len__()&gt;1 %} ... {% endif %}

Although this works, I&#39;m afraid that some future implementation of strings might break this code. Is there a better way to do this?

Length of string in Jinja/Flask

Jinja unfortunately does not support executing arbitrary Python code, such as
<pre><code class="hljs language-scss">{% if len(some_var)>1 %} ... {% endif %}
</code></pre>
My current workaround is to use the deprecated, ugly, double-underscore method:
<pre><code class="hljs language-makefile">{% if some_var.__len__()>1 %} ... {% endif %}
</code></pre>
Although this works, I'm afraid that some future implementation of strings might break this code. Is there a better way to do this?

I hit this TypeError exception recently, which I found very difficult to debug. I eventually reduced it to this small test case:

    &gt;&gt;&gt; &quot;{:20}&quot;.format(b&quot;hi&quot;)
    Traceback (most recent call last):
      File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
    TypeError: non-empty format string passed to object.__format__

This is very non-obvious, to me anyway. The workaround for my code was to decode the byte string into unicode:

     &gt;&gt;&gt; &quot;{:20}&quot;.format(b&quot;hi&quot;.decode(&quot;ascii&quot;))
     &#39;hi                  &#39;

What is the meaning of this exception? Is there a way it can be made more clear?

Python TypeError: non-empty format string passed to object.__format__

Getting this error:

    sudo: unable to resolve host coderw@ll
    -- Could NOT find PythonLibs (missing:  PYTHON_LIBRARIES PYTHON_INCLUDE_DIRS) 
    CMake Error at /usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:108     
    (message):
    Could NOT find PythonInterp (missing: PYTHON_EXECUTABLE)
    Call Stack (most recent call first):
    /usr/share/cmake-2.8/Modules/FindPackageHandleStandardArgs.cmake:315  
    (_FPHSA_FAILURE_MESSAGE)
    /usr/share/cmake-2.8/Modules/FindPythonInterp.cmake:139 
    (FIND_PACKAGE_HANDLE_STANDARD_ARGS)
    Code/cmake/Modules/FindNumPy.cmake:10 (find_package)
    CMakeLists.txt:114 (find_package)



    -- Configuring incomplete, errors occurred!
    See also &quot;/home/coderwall/Desktop/rdkit/build/CMakeFiles/CMakeOutput.log&quot;.
    See also &quot;/home/coderwall/Desktop/rdkit/build/CMakeFiles/CMakeError.log&quot;.

I have already installed:

 1. sudo apt-get install python-dev
 2. Environment variable are already set as follow:

        PYTHON_INCLUDE_DIRS=/usr/include/python2.7 
        PYTHON_LIBRARIES=/usr/lib/python2.7/config/libpython2.7.so

Location of `python.h` : `/usr/lib/include/python2.7/python.h`

Location of `python` libs: `/usr/lib/python2.7/`
How to solve this? 




Cmake is not able to find Python-libraries

I&#39;m trying to install Pandas using pip, but I&#39;m having a bit of trouble.  I just ran `sudo pip install pandas` which successfully downloaded pandas.  However, it did not get downloaded to the location that I wanted.  Here&#39;s what I see when I use `pip show pandas`:

    ---
    Name: pandas
    Version: 0.14.0
    Location: /Library/Python/2.7/site-packages/pandas-0.14.0-py2.7-macosx-10.9-intel.egg
    Requires: python-dateutil, pytz, numpy

So it is installed.  But I was confused when I created a new Python Project and searched under `System Libs/lib/python` for pandas, because it didn&#39;t show up.  Some of the other packages that I&#39;ve downloaded in the past did show up, however, so I tried to take a look at where those were.  Running `pip show numpy` (which I can import with no problem) yielded:

    ---
    Name: numpy
    Version: 1.6.2
    Location: /System/Library/Frameworks/Python.framework/Versions/2.7/Extras/lib/python
    Requires: 

Which is in a completely different directory.  For the sake of confirming my error, I ran `pip install pyquery` to see where it would be downloaded to, and got:

    Name: pyquery
    Version: 1.2.8
    Location: /Library/Python/2.7/site-packages
    Requires: lxml, cssselect

So the same place as pandas...

How do I change the default download location for pip so that these packages are downloaded to the same location that numpy is in?  

Note: There were a few similar questions that I saw when searching for a solution, but I didn&#39;t see anything that mentioned **permanently** changing the default location.

How to change default install location for pip

I use the following simple code to parse some arguments; note that one of them is required. Unfortunately, when the user runs the script without providing the argument, the displayed usage/help text does not indicate that there is a non-optional argument, which I find very confusing. How can I get python to indicate that an argument is not optional?

Here is the code:


    import argparse
    if __name__ == &#39;__main__&#39;:
        parser = argparse.ArgumentParser(
            description=&#39;Foo&#39;)
        parser.add_argument(&#39;-i&#39;,&#39;--input&#39;, help=&#39;Input file name&#39;, required=True)
        parser.add_argument(&#39;-o&#39;,&#39;--output&#39;, help=&#39;Output file name&#39;, default=&quot;stdout&quot;)
        args = parser.parse_args()
        print (&quot;Input file: %s&quot; % args.input )
        print (&quot;Output file: %s&quot; % args.output )

When running above code without providing the required argument, I get the following output:

    usage: foo.py [-h] -i INPUT [-o OUTPUT]

    Foo

    optional arguments:
        -h, --help            show this help message and exit
        -i INPUT, --input INPUT
                              Input file name
        -o OUTPUT, --output OUTPUT
                              Output file name


Argparse: Required arguments listed under &quot;optional arguments&quot;?

I have a DataFrame looking like this:

         amount     price
    age
    A     40929   4066443
    B     93904   9611272
    C    188349  19360005
    D    248438  24335536
    E    205622  18888604
    F    140173  12580900
    G     76243   6751731
    H     36859   3418329
    I     29304   2758928
    J     39768   3201269
    K     30350   2867059

Now I&#39;d like to plot a bar-plot with the age on the x-axis as labels. For each x-tick there should be two bars, one bar for the amount, and one for the price. I can get this working by using simply:

    df.plot(kind=&#39;bar&#39;)

The problem is the scaling. The prices are so much higher that I can not really identify the amount in that graph, see:

![enter image description here][1]

Thus I&#39;d like a second y-axis. I tried it using:

    df.loc[:,&#39;amount&#39;].plot(kind=&#39;bar&#39;)
    df.loc[:,&#39;price&#39;].plot(kind=&#39;bar&#39;,secondary_y=True)

but this just overwrites the bars and does NOT place them side-by-side.
Is there any way to do this without having to access the lower-level matplotlib (which would be possible obviously by placing the bars side by side manually)?

For now, I&#39;m using two single plots within subplots:

    df.plot(kind=&#39;bar&#39;,grid=True,subplots=True,sharex=True); 

resulting in:

![enter image description here][2]


  [1]: http://i.stack.imgur.com/8PZSi.png
  [2]: http://i.stack.imgur.com/oSz6a.png

Pandas: Bar-Plot with two bars and two y-axis

Is there a way to return a response (from `make_response()` object or similar) with certain properties so that it doesn&#39;t render the page again and doesn&#39;t do anything else either. I am trying to run a code on the server without generating any output 

A simple &#39;return None&#39; produces:

    ValueError: View function did not return a response


This should be possible because the following only downloads a file and doesn&#39;t render the template: 

    myString = &quot;First line of a document&quot;
    response = make_response(myString)
    response.headers[&quot;Content-Disposition&quot;] = &quot;attachment; filename=myFile.txt&quot;
    return response


Python Flask Intentional Empty Response

I *have* read [the official Flask documentation](http://flask.pocoo.org/docs/blueprints/) on Blueprints and even [one](http://maximebf.com/blog/2012/11/getting-bigger-with-flask/#.U6ttiZSwK7M) or [two](http://charlesleifer.com/blog/dont-sweat-small-stuff-use-flask-blueprints/) blog posts on using them.

I&#39;ve even used them in my web app, but I don&#39;t completely understand what they are or how they fit into my app as a whole. How is it similar to an instance of my app but not quite? The documentation is comprehensive but I seek a layman explanation or an enlightening analogy to spark it for me. I was sufficiently perplexed when a colleague asked me to explain a Flask blueprint to them that I elected to ask here.

What are Flask Blueprints, exactly?

I&#39;m trying to create a web app with Flask that lets a user upload a file and serve them to another user. Right now, I can upload the file to the *upload_folder* correctly. But I can&#39;t seem to find a way to let the user download it back.

I&#39;m storing the name of the filename into a database. 

I have a view serving the database objects. I can delete them too.

    @app.route(&#39;/dashboard&#39;, methods=[&#39;GET&#39;, &#39;POST&#39;])
    def dashboard():

        problemes = Probleme.query.all()

        if &#39;user&#39; not in session:
            return redirect(url_for(&#39;login&#39;))

        if request.method == &#39;POST&#39;:
            delete = Probleme.query.filter_by(id=request.form[&#39;del_button&#39;]).first()
            db.session.delete(delete)
            db.session.commit()
            return redirect(url_for(&#39;dashboard&#39;))

        return render_template(&#39;dashboard.html&#39;, problemes=problemes)


In my HTML I have:

    &lt;td&gt;&lt;a href=&quot;{{ url_for(&#39;download&#39;, filename=probleme.facture) }}&quot;&gt;Facture&lt;/a&gt;&lt;/td&gt;

and a download view :

    @app.route(&#39;/uploads/&lt;path:filename&gt;&#39;, methods=[&#39;GET&#39;, &#39;POST&#39;])
    def download(filename):
        return send_from_directory(directory=app.config[&#39;UPLOAD_FOLDER&#39;], filename=filename)

But it&#39;s returning : 

&gt; Not Found

The requested URL was not found on the server. If you entered the URL manually please check your spelling and try again.

I just want to link the filename to the object and let the user download it (For every object in the same view) 

Flask Download a File

I have an HTML form with multiple inputs named like this:

&lt;!-- language: lang-html --&gt;

    &lt;input name=&quot;hello[]&quot; type=&quot;text&quot; /&gt;
    &lt;input name=&quot;hello[]&quot; type=&quot;text&quot; /&gt;
    &lt;input name=&quot;hello[]&quot; type=&quot;text&quot; /&gt;

In **PHP** you get this as an array but is it the same way in Python, using Flask?

I have tried this:

    hello = request.form[&#39;hello&#39;]
  
    print(hello)

But that did not work, I got a `400 Bad Request`:

&lt;!-- language: lang-none --&gt;

    Bad Request

    The browser (or proxy) sent a request that this server could not understand.

How do I do it in Flask?

Sending a form array to Flask

When the user accesses this URL running on my flask app, I want the web service to be able to handle the parameters specified after the question mark:

    http://10.1.1.1:5000/login?username=alex&amp;password=pw1

    #I just want to be able to manipulate the parameters
    @app.route(&#39;/login&#39;, methods=[&#39;GET&#39;, &#39;POST&#39;])
    def login():
        username = request.form[&#39;username&#39;]
        print(username)
        password = request.form[&#39;password&#39;]
        print(password)

How can I get the named parameters from a URL using Flask?

I serve dynamic pages from Jinja2 templates in Flask. Now I am defining client-side templates in say, Jinja2-clone Nunjucks inside a script tag. Problem is, the client-side templates has syntax like `&lt;% %&gt;` that *Flask&#39;s* Jinja2 interpreter may interpret instead of rendering *verbatim*.

How can I make the entire block of scripts render verbatim?

Escape jinja2 syntax in a jinja2 template

I tried:

    list1 = [{&quot;username&quot;: &quot;abhi&quot;, &quot;pass&quot;: 2087}]
    return render_template(&quot;file_output.html&quot;, list1=list1)

In the template:

    &lt;table border=2&gt;
      &lt;tr&gt;
        &lt;td&gt;
          Key
        &lt;/td&gt;
        &lt;td&gt;
          Value
        &lt;/td&gt;
      &lt;/tr&gt;
      {% for dictionary in list1 %}
        {% for key in dictionary %}
          &lt;tr&gt;
            &lt;td&gt;
              &lt;h3&gt;{{ key }}&lt;/h3&gt;
            &lt;/td&gt;
            &lt;td&gt;
              &lt;h3&gt;{{ dictionary[key] }}&lt;/h3&gt;
            &lt;/td&gt;
          &lt;/tr&gt;
        {% endfor %}
      {% endfor %}
    &lt;/table&gt;

The above code is splitting each element into multiple characters:

    [
    
    {
    
    &quot;
    
    u
    
    s
    
    e

    r

    ...

I tested the above nested loop in a simple Python script and it works fine but not in Jinja template.


How to iterate through a list of dictionaries in Jinja template?

I have a method that returns data which is needed in my base template (content for a global footer).

How do either (1) pass a variable into the base template (which other templates extend) or (2) pass a variable to all templates globally without explicitly adding it in a call to `render_template`?

Flask + Jinja: Pass Data to a Base Template/All Templates

I have a python dictionary:

    settings = {
       &quot;foo&quot; : &quot;baz&quot;,
       &quot;hello&quot; : &quot;world&quot;
    }

This variable `settings` is then available in the Jinja2 template. 

I want to check if a key `myProperty` exists in the `settings` dict within my template, and if so take some action: 

    {% if settings.hasKey(myProperty) %}
       takeSomeAction();
    {% endif %}

What is the equivalent of `hasKey` that I can use?

Check if key exists in a Python dict in Jinja2 templates

I need to programatically distinguish between Jinja template files, other template files (such as ERB), and template-less plain text files.

According to [Jinja documentation]:

&gt; A Jinja template doesn’t need to have a specific extension: .html, .xml, or any other extension is just fine.

But what should I use when an explicit extension is required? `.py` is misleading, and any search including the words &quot;jinja&quot; and &quot;extension&quot; are badly searchwashed by discussion around [Jinja Extensions].

I could easily dictate a project-wide convention (`.jnj` or `.ja` come to mind) but this is for open source so I don&#39;t want to buck the trend if there&#39;s already established practice somewhere.

---
**EDIT 1:** Again, I understand that the Jinja project &amp;mdash; purposefully &amp;mdash; does not define a default file extension. I&#39;m asking if there are any unofficial conventions that have emerged for circumstances where one is desired for some project-specific reason.

---
**EDIT 2:** Clarification: This is not for HTML content.

[jinja documentation]: http://jinja.pocoo.org/docs/dev/templates/
[jinja extensions]: http://jinja.pocoo.org/docs/dev/extensions/

Is there an idiomatic file extension for Jinja templates?

The data type of the field is String. I would like to fetch the data where character length of field name is greater than 40.

I tried these queries but returning error.
1. 

    db.usercollection.find(
    {$where: &quot;(this.name.length &gt; 40)&quot;}
    ).limit(2);

    output :error: {
    	&quot;$err&quot; : &quot;TypeError: Cannot read property &#39;length&#39; of undefined near &#39;40)&#39; &quot;,
    	&quot;code&quot; : 16722
    }

this is working in 2.4.9 But my version is 2.6.5



String field value length in mongoDB

Does java.util.UUID.randomUUID().toString() length always equal to 36?

I was not able to find info on that. [Here](http://docs.oracle.com/javase/7/docs/api/java/util/UUID.html) it is said only the following: 
&gt;public static UUID randomUUID()
Static factory to retrieve a type 4 (pseudo randomly generated) UUID. The UUID is generated using a cryptographically strong pseudo random number generator.
Returns:
A randomly generated UUID

And that `type 4` tells me nothing. I do not know what type 4 means in the case.

Content Type	Original Author	Original Content on Stackoverflow
Question	wuxiekeji	View Question on Stackoverflow
Solution 1 - Python	Martijn Pieters	View Answer on Stackoverflow

Length of string in Jinja/Flask

Python Problem Overview

Python Solutions

Solution 1 - Python

$skip and $limit in aggregation framework

Angular bootstrap datepicker date format does not format ng-model value

Attributions