    l = ((&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;), &#39;dd&#39;)
    l = l[0] + (l[1],)

This will work for your situation, however [John La Rooy&#39;s solution](https://stackoverflow.com/a/14745275/1907098) is better for general cases.

    a = (1, 2)
    b = (3, 4)

    x = a + b

    print(x)
Out:

    (1, 2, 3, 4)
    



    &gt;&gt;&gt; tuple(j for i in ((&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;), &#39;dd&#39;) for j in (i if isinstance(i, tuple) else (i,)))
    (&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;, &#39;dd&#39;)



    x = ((&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;), &#39;dd&#39;)
    tuple(list(x[0]) + [x[1]])


    l = ((&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;), &#39;dd&#39;)

You can simply do:

    (*l[0], l[1])

Result:

    (&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;, &#39;dd&#39;)

**COMPILER:**  *g++ 4.7.2*

Ok. So I am confused about default parameters in `.h` and `.cpp` files. It is mentioned in many places( including this site) that default parameters can be added only in .h files and not in .cpp files. 
However, this code proves it wrong:

**test1.h**

    #pragma once
    
    #include &lt;iostream&gt;
    using namespace std;
    
    class Class{
    public:
    	Class(int, int, int=1);
    };


**test1.cpp**

    #include &quot;test1.h&quot;
    
    Class::Class(int a, int b=2, int c)
    {
    	cout&lt;&lt;a&lt;&lt;&quot; &quot;&lt;&lt;b&lt;&lt;&quot; &quot;&lt;&lt;c&lt;&lt;endl;
    }
    
    int main()
    {
    	Class a(1);
    	return 0;
    }

Now, according to what I have tested, default parameters can be added to `.cpp` files. However, the following restrictions hold:

 1. The default parameters present in `.cpp` and `.h` file should not
    overlap. i.e. `Class(a, b, c=1)` (in .h file) and
    `Class::Class(a,b,c=2)`( in .cpp file) is invalid.
    
    It is a well known rule that once default parameters have been
    added, all the variables declared after that must also contain
    default values. Lets call this the *defpara* rule. Now,
 2. The variables stated in the function declaration( `.h` file) should
    obey the *defpara* rule i.e. `Class(a, b=2, c)` (in .h file)  is
    invalid irrespective of what&#39;s declared in .cpp file.

 3. If one considers the variables having default values (as an
    intersection of default values in `.h` and `.cpp` files), it would
    follow the *defpara* rule. i.e. `Class(a, b, c=1)` (in .h file) and
    `Class::Class(a,b=2,c)`( in `.cpp` file) is valid. But `Class(a, b,
    c=1)` (in .h file) and `Class::Class(a=2,b,c)`( in `.cpp` file) is
    invalid.


So....I am right, wrong???

default parameters in .h and .cpp files

I want to have a binary operator `cross` (cross-product/cartesian product) that operates with traversables in Scala:

    val x = Seq(1, 2)
    val y = List(&#39;hello&#39;, &#39;world&#39;, &#39;bye&#39;)
    val z = x cross y    # i can chain as many traversables e.g. x cross y cross w etc
    
    assert z == ((1, &#39;hello&#39;), (1, &#39;world&#39;), (1, &#39;bye&#39;), (2, &#39;hello&#39;), (2, &#39;world&#39;), (2, &#39;bye&#39;))

What is the best way to do this in Scala only (i.e. not using something like scalaz)?

Cross product in Scala

How to convert the following  tuple:

from:

    ((&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;), &#39;dd&#39;)

to:


    (&#39;aa&#39;, &#39;bb&#39;, &#39;cc&#39;, &#39;dd&#39;)



How to destack nested tuples in Python?

How to convert the following tuple:
from:
<pre><code class="hljs language-arduino">(('aa', 'bb', 'cc'), 'dd')
</code></pre>
to:
<pre><code class="hljs language-arduino">('aa', 'bb', 'cc', 'dd')
</code></pre>

Is there an easy way in Python to check whether the value of an optional parameter comes from its default value, or because the user has set it explicitly at the function call?

How to check whether optional function parameter is set

Imagine having 2 numpy arrays:

    &gt; A, A.shape = (n,p)
    &gt; B, B.shape = (p,p)

Typically p is a smaller number (p &lt;= 200), while n can be arbitrarily large.

I am doing the following:

    result = np.diag(A.dot(B).dot(A.T))

As you can see, I am keeping only the n diagonal entries, however there is an intermediate (n x n) array calculated from which only the diagonal entries are kept.

I wish for a function like diag_dot(), which only calculates the diagonal entries of the result and does not allocate the complete memory.

A result would be:

    &gt; result = diag_dot(A.dot(B), A.T)

Is there a premade functionality like this and can this be done efficiently without the need for allocating the intermediate (n x n) array?

Is there a numpy/scipy dot product, calculating only the diagonal entries of the result?

I can add a y label to the left y-axis using `plt.ylabel`, but how can I add it to the secondary y-axis?


    table = sql.read_frame(query,connection)

    table[0].plot(color=colors[0],ylim=(0,100))
    table[1].plot(secondary_y=True,color=colors[1])
    plt.ylabel(&#39;$&#39;)





Adding a y-axis label to secondary y-axis in matplotlib

See the following code: 

    import datetime
    import pytz
    
    fmt = &#39;%Y-%m-%d %H:%M:%S %Z&#39;
    
    d = datetime.datetime.now(pytz.timezone(&quot;America/New_York&quot;))
    d_string = d.strftime(fmt)
    d2 = datetime.datetime.strptime(d_string, fmt)
    print d_string 
    print d2.strftime(fmt)

the output is 

    2013-02-07 17:42:31 EST
    2013-02-07 17:42:31 

The timezone information simply got lost in the translation. 

If I switch &#39;%Z&#39; to &#39;%z&#39;, I get

    ValueError: &#39;z&#39; is a bad directive in format &#39;%Y-%m-%d %H:%M:%S %z&#39;

I know I can use `python-dateutil`, but I just found it bizzare that I can&#39;t achieve this simple feature in datetime and have to introduce more dependency? 




Python datetime strptime() and strftime(): how to preserve the timezone information

Is there a Pythonic and efficient way to check whether a Numpy array contains at least one instance of a given row?  By &quot;efficient&quot; I mean it terminates upon finding the first matching row rather than iterating over the entire array even if a result has already been found.

With Python arrays this can be accomplished very cleanly with `if row in array:`, but this does not work as I would expect for Numpy arrays, as illustrated below.

With Python arrays:

    &gt;&gt;&gt; a = [[1,2],[10,20],[100,200]]
    &gt;&gt;&gt; [1,2] in a
    True
    &gt;&gt;&gt; [1,20] in a
    False

but Numpy arrays give different and rather odd-looking results. (The `__contains__` method of `ndarray` seems to be undocumented.)

    &gt;&gt;&gt; a = np.array([[1,2],[10,20],[100,200]])
    &gt;&gt;&gt; np.array([1,2]) in a
    True
    &gt;&gt;&gt; np.array([1,20]) in a
    True
    &gt;&gt;&gt; np.array([1,42]) in a
    True
    &gt;&gt;&gt; np.array([42,1]) in a
    False


testing whether a Numpy array contains a given row

What I try to do is this:

    public class History {
    	public class State {
    		public enum StateType {

Eclipse gives me this compile error on `StateType`: `The member enum StateType must be defined inside a static member type`.

The error disappears when I make the `State` class static. I could make `State` static, but I don&#39;t understand why I cannot declare an `enum` in an inner class.

Why can&#39;t I create an enum in an inner class in Java?

I have a problem when querying mongoDB with nested objects notation:

    db.messages.find( { headers : { From: &quot;reservations@marriott.com&quot; } } ).count()
    0
    db.messages.find( { &#39;headers.From&#39;: &quot;reservations@marriott.com&quot; }  ).count()
    5

I can&#39;t see what I am doing wrong. I am expecting nested object notation to return the same result as the dot notation query. Where am I wrong?

How to query nested objects?

I&#39;m very new to python and I wish I could do `.` notation to access values of a `dict`. 

Lets say I have `test` like this:

    &gt;&gt;&gt; test = dict()
    &gt;&gt;&gt; test[&#39;name&#39;] = &#39;value&#39;
    &gt;&gt;&gt; print(test[&#39;name&#39;])
    value

But I wish I could do `test.name` to get `value`. Infact I did it by overriding the `__getattr__` method in my class like this:

    class JuspayObject:

    	def __init__(self,response):
	    	self.__dict__[&#39;_response&#39;] = response

        def __getattr__(self,key): 
        	try:
    	    	return self._response[key]
    	    except KeyError,err:
    	    	sys.stderr.write(&#39;Sorry no key matches&#39;)

and this works! when I do:

    test.name // I get value.

But the problem is when I just print `test` alone I get the error as:

    &#39;Sorry no key matches&#39;

Why is this happening?
		

How to use dot notation for dict in python?

I have 2 CSV files: &#39;Data&#39; and &#39;Mapping&#39;:

 - &#39;Mapping&#39; file has 4 columns: `Device_Name`, `GDN`, `Device_Type`, and `Device_OS`. All four columns are populated.
 - &#39;Data&#39; file has these same columns, with `Device_Name` column populated and the other three columns blank. 
 - I want my Python code to open both files and for each `Device_Name` in the Data file, map its `GDN`, `Device_Type`, and `Device_OS` value from the Mapping file.

I know how to use dict when only 2 columns are present (1 is needed to be mapped) but I don&#39;t know how to accomplish this when 3 columns need to be mapped.

Following is the code using which I tried to accomplish mapping of `Device_Type`:

    x = dict([])
    with open(&quot;Pricing Mapping_2013-04-22.csv&quot;, &quot;rb&quot;) as in_file1:
        file_map = csv.reader(in_file1, delimiter=&#39;,&#39;)
        for row in file_map:
           typemap = [row[0],row[2]]
           x.append(typemap)
    
    with open(&quot;Pricing_Updated_Cleaned.csv&quot;, &quot;rb&quot;) as in_file2, open(&quot;Data Scraper_GDN.csv&quot;, &quot;wb&quot;) as out_file:
        writer = csv.writer(out_file, delimiter=&#39;,&#39;)
        for row in csv.reader(in_file2, delimiter=&#39;,&#39;):
             try:
                  row[27] = x[row[11]]
             except KeyError:
                  row[27] = &quot;&quot;
             writer.writerow(row)

It returns `Attribute Error`.

After some researching, I think I need to create a nested dict, but I don&#39;t have any idea how to do this.  

How do you create nested dict in Python?

I&#39;m building a **User Class** for my new website, however this time I was thinking to build it little bit differently...

**C++**, **Java** and even **Ruby** (and probably other programming languages) are allowing the use of nested/inner classes inside the main class, which allows us to make the code more object-oriented and organized.

In PHP, I would like to do something like so:

    &lt;?php
      public class User {
        public $userid;
        public $username;
        private $password;
    
        public class UserProfile {
          // some code here
        }
    
        private class UserHistory {
          // some code here
        }
      }
    ?&gt;

Is that possible in PHP? How can I achieve it?
&lt;hr&gt;

**UPDATE**

If it&#39;s impossible, will future PHP versions might support nested classes?

Nested or Inner Class in PHP

I want to find the minimum of a list of tuples sorting by a given column.  I have some data arranged as a list of 2-tuples for example.

    data = [ (1, 7.57), (2, 2.1), (3, 1.2), (4, 2.1), (5, 0.01), 
             (6, 0.5), (7, 0.2), (8, 0.6)]

How may I find the min of the dataset by the comparison of the second number in the tuples only?

i.e. 

    data[0][1] = 7.57
    data[1][1] = 2.1

min( data ) = `(5, 0.01)`


`min( data )` returns `(1, 7.57)`, which I accept is correct for the minimum of index 0, but I want minimum of index 1.



Tuple pairs, finding minimum using python

I&#39;m still a little new to this, so I might not know all the conventional terms for things:

Is it possible to preserve Python tuples when encoding with JSON?  Right now `json.loads(json.dumps(tuple))` gives me a list back.  I don&#39;t want to convert my tuples to lists, but I want to use JSON.  So, are there options?


The reason why:
I&#39;m creating an app that uses multi-dimensional arrays, not always the same shape.  I&#39;ve got some class methods that use recursion to probe the arrays and cast the endpoints as a string or int.  I recently realized that (based on how my recursion works) I can use tuples to prevent deeper recursive searching of arrays (Python rawks).  This could come in handy in situations where I know I for sure I won&#39;t need to be probing any deeper into my data structures.

Preserve Python tuples with JSON

Is there a reference somewhere defining precisely when enclosing tuples with parentheses is or is not required?  

Here is an example that surprised me recently:


    &gt;&gt;&gt; d = {}
    &gt;&gt;&gt; d[0,] = &#39;potato&#39;
    &gt;&gt;&gt; if 0, in d:
      File &quot;&lt;stdin&gt;&quot;, line 1
        if 0, in d:
            ^
    SyntaxError: invalid syntax



When are parentheses required around a tuple?

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.

Content Type	Original Author	Original Content on Stackoverflow
Question	Cory	View Question on Stackoverflow
Solution 1 - Python	Volatility	View Answer on Stackoverflow
Solution 2 - Python	Thirumal Alagu	View Answer on Stackoverflow
Solution 3 - Python	John La Rooy	View Answer on Stackoverflow
Solution 4 - Python	xvorsx	View Answer on Stackoverflow
Solution 5 - Python	Luna	View Answer on Stackoverflow

How to destack nested tuples in Python?

Python Problem Overview

Python Solutions

Solution 1 - Python

Solution 2 - Python

Solution 3 - Python

Solution 4 - Python

Solution 5 - Python

Cross product in Scala

default parameters in .h and .cpp files

Attributions