Python tutorial -- #2 (Garbage Collector, Comment, Variables and Datatypes)

Python tutorial

GARBAGE COLLECTOR (GC)

Module =  A module is a code that can perform an specific task.

>>> In Python GC (Garbage Collector) is a module that helps to remove the unwanted things during the execution. When a program execution takes place GC generate a reference count to each object. Reference count means how many times the object execute. when an object has reference count of at least 1 then GC do not removes them but when an object has reference count of 0 then GC understands that object has not any use in program and GC removes them. Python tutorial

In the given figure A, B and C are three object. when we execute this program then Python interpreter interprate from A object to B object and then execute C after that it passed to A object. Thus, A, B and C has reference count of 1. So, GC not removes them.

COMMENT

Observe the given program :-

The First line of this program starts with #. This symbol represents comment line. Comment line are used to describe the feature of program. It makes the program more understandable (Readable). When programmer work on big project where more then one people involves then describing comment becomes very essential because more than 1 people are involved in programming. So, They all can understands the program are possible only by describing comments.Python tutorial

>>> Comment are of two types :-

 i) Single line comments

ii) Multi line comments

➠Single line comments = This comment starts with # symbol and do not end till the the line changed.

Example :-

➠Multi line comment = Multi line comment are the comment which can expand more than one lines.

It is represented by triple single quote (''' ''') or triple double quote (""" """).

Example :-

Actually, there is not any multi line comment, It is just a string value with the exception that it can expand into multi line. Thus, There is not any multi line comment this is the string value and it also acquire space in memory. But it is not stored in any variable and hence, G.C removes them and we can use them as multi line comment. But many programmer do not use this because it wastes the time of interpreter.Python tutorial

HOW PYTHON SEES VARIABLES

In other Programming languages like C, Java etc. Variables is connected to memory location. It is imagined that memory location is just like a storage box in which value is stored.

For example:- A= 1

When there is a new value assigned to variables then new value assigned in the storage box and old value is removed by Garbage Collector(GC).

For example:- A =2

and when a new variable is assigned in the old variable then a new memory location (storage box) is created which store the value of the old variable.

For example:- A = B

But in Python, it is quite different. In Python, Variable is seen as a tag(or name) that is tied to some value.

For example:- A = 1

Here there is a value (1) that is tied by a name 'A'.

When we assigned a new value to the variable in Python then the new value is tied with the variable name and old value is removed by G.C.

For example:- A = 2

and when we assigned a new variable in the old variable then the value of variable is tied with two variable name.

For example:- A = B

 DATATYPE IN PYTHON

➤Datatype represents the type of data that are stored in variable (or memory).Python tutorial

➧There are two type of data in variable.

i)  Built in datatype

ii) User defined datatype

⧭Built in datatype are subdivide into five types :--

⤷ None type 

⤷ Numeric type

⤷ Sequence type

⤷ Set type

⤷ Mapping type

➣None type datatype = This datatype represents an object which do not contain any value. It is also called Null datatype.

➣Numeric datatype = This datatype represents the number. There are three sub types :-

⤷Integer

⤷Float

⤷Complex

➪Integer datatype = All the integer number (numeric without fraction or decimal) are represented by Integer datatype.

➪Float datatype = All the decimal value are represented by Float datatype.

➪Complex datatype = The number which are of the form of a+bj where j = -1^1/2 are called complex number. and all the complex number are represented by complex datatype.

Example :-

➣Sequence datatype = Sequence datatype are the type of datatype which contains the group of element. It is subdivided into six types :-
⤷ String
⤷ Bytes
⤷ Bytearray
⤷ List
⤷ Tuple
⤷ Range

➪String = This datatype are represented by 'str' and it contains the string value.

Example :-

➪Bytes = This datatype contains the integer value from 0 to 255 (inclusive). But we cannot do any modification in this datatypes.

➪Bytearray = Bytearray datatype are similar to bytes datatype. But in this datatype we can do various modifications.

➪List = A list represents a group of elements and it is denoted by square brackets ([]) and elements are written in square brackets ([]), separated by commas. For example :-

➪Tuple = A tuple is similar to list and it is represented by small brackets (). and elements are written in it  and separated by commas.
        we cannot do any modification in Tuple whereas we can do various modifications in List datatype. 

Example:-

➪Range = The range datatype represents a sequence of numbers. The numbers in range are not modifiable. Generally, Range is used for repeating a for loop for a specific numbers of time. To create a range of numbers we can take an example:- 

Here, The range object is created with the numbers starting from 0 to 9. we can display these numbers using a for loop as :-

➣Sets datatype = This datatype contains a group of elements separated by commas. inside the middle braces ({}). and it doesn't accepts duplicate elements. moreover, order of element is not maintained in the sets. It means element may not appear in the same order as they entered into the set.Python tutorial

➧There are two sub types:-

⤷Set datatype     
⤷Frozenset datatype

➭Set and Frozenset datatype are similar to each other. The only difference is that in the set datatype we can do modifications whereas frozenset datatype cannot be modified.

➣Mapping Type = A map represents a group of elements in the form of Keys values pair. So, that when the key is given we can retrieve the value associated with it.

                                                  Dict datatype is an example of Map.

➭Dict datatype = The 'Dict' represents 'Dictionary' that contains pairs of elements such that the first element represents the key and next one becomes its value. The key and its value should be separated by a colon (:) and every pair should be separated by a comma. All the elements should be enclosed inside curly bracket ({}).

Example:-

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End line ---- Hope this series of Python tutorial is beneficial for you guys....