The signature of [`set.union`][1] is `union(other, ...)`. Unpack sets from your list:

    In [6]: set.union(*x)
    Out[6]: {1, 2, 3, 4, 5}


  [1]: https://docs.python.org/3/library/stdtypes.html#set.union

Interactively, I can use &quot;aws configure&quot; to change or see the default region. Is there a &quot;pwd&quot; like function, documented or not that allows me to determine or confirm the current region mid-script ? Even if AWS_DEFAULT_REGION is not defined ? I want a script to run under a number of profiles. I can scrape from aws configure list, but is there something neater ?

Using aws cli, what is best way to determine the current region

How to give more column conditions when joining two dataframes. For example I want to run the following :

    val Lead_all = Leads.join(Utm_Master,  
        Leaddetails.columns(&quot;LeadSource&quot;,&quot;Utm_Source&quot;,&quot;Utm_Medium&quot;,&quot;Utm_Campaign&quot;) ==
        Utm_Master.columns(&quot;LeadSource&quot;,&quot;Utm_Source&quot;,&quot;Utm_Medium&quot;,&quot;Utm_Campaign&quot;),
    &quot;left&quot;)

I want to join only when these columns match. But above syntax is not valid as cols only takes one string. So how do I get what I want.


Spark specify multiple column conditions for dataframe join

This is the input:  

    x = [{1, 2, 3}, {2, 3, 4}, {3, 4, 5}]

and the output should be:

    {1, 2, 3, 4, 5}

I tried to use `set().union(x)` but this is the error I&#39;m getting:

&lt;!-- language: lang-none --&gt;

    Traceback (most recent call last):
      File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
    TypeError: unhashable type: &#39;set&#39;



How can I find the union on a list of sets in Python?

This is the input:
<pre><code class="hljs language-ini">x = [{1, 2, 3}, {2, 3, 4}, {3, 4, 5}]
</code></pre>
and the output should be:
<pre><code class="hljs">{1, 2, 3, 4, 5}
</code></pre>
I tried to use <code>set().union(x)</code> but this is the error I'm getting:

<pre><code class="hljs language-arduino">Traceback (most recent call last):
 File "&#x3C;stdin>", line 1, in &#x3C;module>
TypeError: unhashable type: 'set'
</code></pre>

I&#39;m currently developing a Python application on which I want to see real-time statistics. I wanted to use `Flask` in order to make it easy to use and to understand.

The issue is that my Flask server should start at the very beginning of my Python application and stop at the very end. It should look like this:

    def main():
        &quot;&quot;&quot; My main application &quot;&quot;&quot;
        from watcher.flask import app
        # watcher.flask define an app as in the Quickstart flask documentation.
        # See: http://flask.pocoo.org/docs/0.10/quickstart/#quickstart

        app.run() # Starting the flask application

        do_my_stuff()

        app.stop() # Undefined, for the idea 

Because I need my application context (for the statistics), I can&#39;t use a `multiprocessing.Process`. Then I was trying to use a `threading.Thread`, but it looks like Werkzeug doesn&#39;t like it: 

     * Running on http://0.0.0.0:10079/
    Exception in thread Flask Server:
    Traceback (most recent call last):
      File &quot;/usr/lib/python2.7/threading.py&quot;, line 810, in __bootstrap_inner
        self.run()
      File &quot;/usr/lib/python2.7/threading.py&quot;, line 763, in run
        self.__target(*self.__args, **self.__kwargs)
      File &quot;.../develop-eggs/watcher.flask/src/watcher/flask/__init__.py&quot;, line 14, in _run
        app.run(host=HOSTNAME, port=PORT, debug=DEBUG)
      File &quot;.../eggs/Flask-0.10.1-py2.7.egg/flask/app.py&quot;, line 772, in run
        run_simple(host, port, self, **options)
      File &quot;.../eggs/Werkzeug-0.7-py2.7.egg/werkzeug/serving.py&quot;, line 609, in run_simple
        run_with_reloader(inner, extra_files, reloader_interval)
      File &quot;.../eggs/Werkzeug-0.7-py2.7.egg/werkzeug/serving.py&quot;, line 524, in run_with_reloader
        signal.signal(signal.SIGTERM, lambda *args: sys.exit(0))
    ValueError: signal only works in main thread


How can I do that without running Flask in the main thread?

Start a flask application in separate thread

I&#39;m having trouble applying upper case to a column in my DataFrame.

dataframe is `df`.

`1/2 ID` is the column head that need to apply UPPERCASE.

The problem is that the values are made up of three letters and three numbers. For example `rrr123` is one of the values.

    df[&#39;1/2 ID&#39;] = map(str.upper, df[&#39;1/2 ID&#39;])

 I got an error:

 `TypeError: descriptor &#39;upper&#39; requires a &#39;str&#39; object but received a &#39;unicode&#39; error.`

How can I apply upper case to the first three letters in the column of the DataFrame `df`?

Applying uppercase to a column in pandas dataframe

I&#39;m trying to create a virtualenv with `virtualenvwrapper`, but when I use `mkvirtualenv` I get the following :

    ERROR: virtualenvwrapper could not find virtualenv in your path

I assumed it was a **PYTHONPATH** problem.
But if I do a `pip show virtualenv` I get the following :

    ---
    Metadata-Version: 2.0
    Name: virtualenv
    Version: 13.1.0
    Summary: Virtual Python Environment builder
    Home-page: https://virtualenv.pypa.io/
    Author: Jannis Leidel, Carl Meyer and Brian Rosner
    Author-email: python-virtualenv@groups.google.com
    License: MIT
    Location: /Volumes/Data/nfs/zfs-student-3/users/2013_paris/vmonteco/Library/Python/2.7/lib/python/site-packages
    Requires:

And here is my **PYTHONPATH** :

*/nfs/zfs-student-3/users/2013_paris/vmonteco/Library/Python/2.7/bin:/nfs/zfs-student-3/users/2013_paris/vmonteco/Library/Python/2.7/bin:/nfs/zfs-student-3/users/2013_paris/vmonteco/Library/Python/2.7/lib/python/site-packages:/Volumes/Data/nfs/zfs-student-3/users/2013_paris/vmonteco/Library/Python/2.7/lib/python/site-packages:~/.brew/Cellar*

It contains the directory containing virtualenv!

(i-e : **/Volumes/Data/nfs/zfs-student-3/users/2013_paris/vmonteco/Library/Python/2.7/lib/python/site-packages** )

My **~/.zshrc** contains :

    export WORKON_HOME=~/Envs
    export PROJECT_HOME=$HOME/Devel
    source $HOME&quot;/Library/Python/2.7/bin/virtualenvwrapper.sh&quot;


**EDIT :**
virtualenvwrapper.sh is written in bash, perhaps should I check my **PATH** instead of my **PYTHONPATH** ?


So, what could the problem be? How could I fix it?

Thank you in advance for your help.


ERROR: virtualenvwrapper could not find virtualenv in your path

I have a project having the structure

    /example
    ../prediction
    ....__init__.py
    ....a.py

PYTHONPATH is pointed to /example

now I open the python in terminal and type

    import prediction

it succeeded, but if I type

    import prediction.a

it returns error

    ImportError: No module named &#39;prediction.a&#39;; &#39;prediction&#39; is not a package

why is that? isn&#39;t that already imported as a package

Import error, No module named xxxx

How can I get the total number of hours in a Pandas timedelta?

For example:

    &gt;&gt;&gt; td = pd.Timedelta(&#39;1 days 2 hours&#39;)
    &gt;&gt;&gt; td.get_total_hours()
    26

Note: as per the documentation, the `.hours` attribute will return the hours *component*:

    &gt;&gt;&gt; td.hours
    2

Get total number of hours from a Pandas Timedelta?

I have two boolean lists, e.g.,

    x=[True,True,False,False]
    y=[True,False,True,False]

I want to AND these lists together, with the expected output:

    xy=[True,False,False,False]

I thought that expression `x and y` would work, but came to discover that it does not: in fact, `(x and y) != (y and x)`

Output of `x and y`: `[True,False,True,False]`

Output of `y and x`: `[True,True,False,False]`

Using list comprehension *does* have correct output. Whew!

    xy = [x[i] and y[i] for i in range(len(x)]

Mind you I could not find any reference that told me the AND operator would work as I tried with x and y. But it&#39;s easy to try things in Python.
Can someone explain to me what is happening with `x and y`?

And here is a simple test program:

    import random
    random.seed()
    n = 10
    x = [random.random() &gt; 0.5 for i in range(n)]
    y = [random.random() &gt; 0.5 for i in range(n)]
    # Next two methods look sensible, but do not work
    a = x and y
    z = y and x
    # Next: apparently only the list comprehension method is correct
    xy = [x[i] and y[i] for i in range(n)]
    print &#39;x        : %s&#39;%str(x)
    print &#39;y        : %s&#39;%str(y)
    print &#39;x and y  : %s&#39;%str(a)
    print &#39;y and x  : %s&#39;%str(z)
    print &#39;[x and y]: %s&#39;%str(xy)


Python AND operator on two boolean lists - how?

I&#39;ve got two lists that I want to merge into a single array and finally put it in a csv file. I&#39;m a newbie with Python arrays and I don&#39;t understand how I can avoid this error :

    def fill_csv(self, array_urls, array_dates, csv_file_path):
        result_array = []
        array_length = str(len(array_dates))
    
        # We fill the CSV file
        file = open(csv_file_path, &quot;w&quot;)
        csv_file = csv.writer(file, delimiter=&#39;;&#39;, lineterminator=&#39;\n&#39;)
    
        # We merge the two arrays in one
    
        for i in array_length:
            result_array[i][0].append(array_urls[i])
            result_array[i][1].append(array_dates[i])
            i += 1
    
        csv_file.writerows(result_array)

And got :

      File &quot;C:\Users\--\gcscan.py&quot;, line 63, in fill_csv
        result_array[i][0].append(array_urls[i])
    TypeError: list indices must be integers or slices, not str

How can my count work ?

TypeError: list indices must be integers or slices, not str

Given the following dictionary:

    dct = {&#39;a&#39;:3, &#39;b&#39;:3,&#39;c&#39;:5,&#39;d&#39;:3}

How can I apply these values to a list such as:

    lst = [&#39;c&#39;, &#39;d&#39;, &#39;a&#39;, &#39;b&#39;, &#39;d&#39;]

in order to get something like:

    lstval = [5, 3, 3, 3, 3]



Mapping dictionary value to list

I have a pandas data frame like this:

       Column1  Column2  Column3  Column4  Column5
     0    a        1        2        3        4
     1    a        3        4        5
     2    b        6        7        8
     3    c        7        7        

What I want to do now is getting a new dataframe containing Column1 and a new columnA. This columnA should contain all values from columns 2 -(to) n (where n is the number of columns from Column2 to the end of the row) like this:

      Column1  ColumnA
    0   a      1,2,3,4
    1   a      3,4,5
    2   b      6,7,8
    3   c      7,7
How could I best approach this issue? Any advice would be helpful. Thanks in advance!

Merge multiple column values into one column in python pandas

When a Python list is known to always contain a single item, is there a way to access it other than:

    mylist[0]

You may ask, &#39;Why would you want to?&#39;. Curiosity alone. There seems to be an alternative way to do *everything* in Python.

Getting only element from a single-element list in Python?

I know of these two questions about `__init__.py` and `__main__.py`:

https://stackoverflow.com/questions/448271

https://stackoverflow.com/questions/4042905

But I don&#39;t really understand the difference between them. Or I could say I don&#39;t understand how they interact together.

What is the difference between __init__.py and __main__.py?

There is a `-&gt;`, or dash-greater-than symbol at the end of a python method, and I&#39;m not sure what it means. One might call it an arrow as well.

Here is the example:


    @property
    def get_foo(self) -&gt; Foo:
        return self._foo

where `self._foo` is an instance of Foo. 

My guess is that it is some kind of static type declaration, to tell the interpreter that `self._foo` is of type Foo. But when I tested this, if `self._foo` is not an instance of Foo, nothing unusual happens. Also, if `self._foo` is of a type other than Foo, let&#39;s say it was an `int`, then `type(SomeClass.get_foo())` returns `int`. So, what&#39;s the point of `-&gt; Foo`?

This concept is hard to lookup because it is a symbol without a common name, and the term &quot;arrow&quot; is misleading.


What does the -&gt; (dash-greater-than arrow symbol) mean in a Python method signature?

Why does Python 3 allow &quot;00&quot; as a literal for 0 but not allow &quot;01&quot; as a literal for 1? Is there a good reason? This inconsistency baffles me. (And we&#39;re talking about Python 3, which purposely broke backward compatibility in order to achieve goals like consistency.)

For example:

    &gt;&gt;&gt; from datetime import time
    &gt;&gt;&gt; time(16, 00)
    datetime.time(16, 0)
    &gt;&gt;&gt; time(16, 01)
      File &quot;&lt;stdin&gt;&quot;, line 1
        time(16, 01)
                  ^
    SyntaxError: invalid token
    &gt;&gt;&gt;

Why does Python 3 allow &quot;00&quot; as a literal for 0 but not allow &quot;01&quot; as a literal for 1?

Is there a simple way to merge ES6 Maps together (like `Object.assign`)? And while we&#39;re at it, what about ES6 Sets (like `Array.concat`)?

Simplest way to merge ES6 Maps/Sets?

`new Set([&#39;b&#39;, &#39;a&#39;, &#39;c&#39;]).sort()` throws `TypeError: set.sort is not a function`. How can I sort a `Set` to ensure a particular iteration order?

How can I sort an ES6 `Set`?

Is there any way to `map`/`reduce`/`filter`/etc a `Set` in JavaScript or will I have to write my own?

Here&#39;s some sensible `Set.prototype` extensions

    Set.prototype.map = function map(f) {
      var newSet = new Set();
      for (var v of this.values()) newSet.add(f(v));
      return newSet;
    };
    
    Set.prototype.reduce = function(f,initial) {
      var result = initial;
      for (var v of this) result = f(result, v);
      return result;
    };
    
    Set.prototype.filter = function filter(f) {
      var newSet = new Set();
      for (var v of this) if(f(v)) newSet.add(v);
      return newSet;
    };
    
    Set.prototype.every = function every(f) {
      for (var v of this) if (!f(v)) return false;
      return true;
    };
    
    Set.prototype.some = function some(f) {
      for (var v of this) if (f(v)) return true;
      return false;
    };

Let&#39;s take a little set

    let s = new Set([1,2,3,4]);

And some stupid little functions

    const times10 = x =&gt; x * 10;
    const add = (x,y) =&gt; x + y;
    const even = x =&gt; x % 2 === 0;

And see how they work

    s.map(times10);    //=&gt; Set {10,20,30,40}
    s.reduce(add, 0);  //=&gt; 10
    s.filter(even);    //=&gt; Set {2,4}
    s.every(even);     //=&gt; false
    s.some(even);      //=&gt; true

&gt; Isn&#39;t that nice ? Yeah, I think so too. Compare that to the ugly iterator usage

    // puke
    let newSet = new Set();
    for (let v in s) {
      newSet.add(times10(v));
    }

And

    // barf
    let sum = 0;
    for (let v in s) {
      sum = sum + v;
    }

Is there any better way to accomplish `map` and `reduce` using a `Set` in JavaScript?

How to map/reduce/filter a Set in JavaScript?

Is it a fair assumption that in v8 implementation retrieval / lookup is O(1)?

(I know that the standard doesn&#39;t guarantee that)



es6 Map and Set complexity, v8 implementation

I&#39;m trying to solve &quot;The go programming lanaguage&quot; exercise #1.4 which requires me to have a set. I can create a set type but why doesn&#39;t the language come with one ? go, having come from google, where guava also originated, why didn&#39;t the language designers opt for adding support for fundamental data structures ? why force your users to create their own implementations for something so basic as a set ?

Content Type	Original Author	Original Content on Stackoverflow
Question	Ravit	View Question on Stackoverflow
Solution 1 - Python	vaultah	View Answer on Stackoverflow

How can I find the union on a list of sets in Python?

Python Problem Overview

Python Solutions

Solution 1 - Python

Spark specify multiple column conditions for dataframe join

Using aws cli, what is best way to determine the current region

Attributions