Python

To chek if list A is completely included in list B – all elements of list A are present in list B, we can use the “superset” and “subset” methods of the standard Python “set” class.

Converting lists to sets also allows us not to worry about checking for duplicates if they exist in the compared lists.

subset

The “subset” method acts on a smaller set and checks if it is in a larger set.

Checking if list A is in list BRead More »

To get information about the operating system, on which our code is executed, we can use the “platform” module.

system

The system() method of this moduel returns the text name of the operating system:

Python: get information about current operating systemRead More »

In order to reduce the size of a long text string, for example, to minimize traffic when sending some text data over the Internet, it can be compressed before sending and unzipped after receiving. The size of transmitted data is significantly reduced in comparison with sending text strings in their original format.

To zip a text string in memory, we can use the “zlib” module.

Let’s use the “compress” function to compress the string. This function takes a byte string as an input parameter and returns the compressed byte string.

As we can see with this simplest example, the line size has been reduced by more than one and a half times.

Python: how to zip a text stringRead More »

To get the first element found in a list by some condition or None if nothing was found we can use the following construction:

With nothing found it returns None:

 

To check what version of the Python interpreter is using to execute code, you can use the “version_info” command from the “sys” module:

In this example the Python version 3.5.2. is using.

The list of classes defined in the * .py file can be obtained using the built-in module “inspect”.

For example, for the “test_cls” module:

we can get a list of classes with the following code:

 

If we have a list:

in order to go through the elements of this list in pairs from the current to the next, we can use the following code:

Results:

 

Some functions take in their parameters a variable number of arguments *args, for example, the itertools.product function.

In order to pass the list as the parameters to this function, we need to use the * operator:

 

Conversion of a string with both individual numbers and ranges of numbers to the list of integer values can be made as follows:

For example a line:

Split the line by comma delimiter:

Let’s split the resulting list into two lists. In the first list, we put only the individual values. In the second – the values got from the ranges of numbers.

Combine the lists into one and drop the duplicate values.

Complete code:

 

To shift values in a list (replace the value at the first place of the list to its last place and vice versa), you need to rearrange the list with two slices.

The shift for the list:

forward:

and backward:

If a cyclic shift is necessary, repeat this command the required number of times in “for” cycle.

Each object’s class to be stored in JSON in a convenient for viewing way must have the __repr__ function, which returns the text representation of the object.

The dictionary with objects:

Saving the dictionary to JSON:

 

Tuples in python can be nested.

If simply add one tuple to another through the concatenation operation “+”, python will merge the values of the tuples:

In order an added tuple to become nested, put a comma “,” after an added tuple:

 

Obtaining the “centroid” – convex polygon central point coordinates, from polygons points (vertices) coordinates:

The input function parameter is a tuple with coordinates of the polygon points. The function returns a tuple with the centroid coordinates:

 

One of the for loops features in Python is that the iterated variable (counter) does not belong to the local scope of the loop.

For example, after executing the following code:

The “a” variable declared before the for loop will change its value if the variable with the same name “a”  declared as the loop counter.

It is necessary to remember about this feature, in order to avoid writing to the previously declared variable the values of the iterator of the for loop.