Identifiers,variables,Reserved words.

gobi2023 — Sun, 15 Nov 2026 15:18:22 +0000

*Identifiers *
A name in python program is known as identifier/variables or reference variables

Rules for identifiers in Python

The first character is a letter (a-z, A-Z) or an underscore _.
The remaining characters are letters, digits 0-9 or underscores.
It can’t be one of the reserved keywords
Case matters: total and Total are consider as two different names.
There’s no length limit.

Name='gobi' //name is identifier
isStudent= True //isStudent is identifier
Rollno=12  //Rollno is identifier

can start with underscore() and double underscore(_)

_name='gobi' //single underscore is also known as  private
__rollno=13 //double underscore is also known as strictly private

Reserved Words or Keywords

we can't use the keywords as identifier or variables.

import keyword
print("The list of keywords are : ")
print(keyword.kwlist)

output:
The list of keywords are: 
['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

Starting Python.....

gobi2023 — Sun, 15 Nov 2026 01:02:09 +0000

Python is General Purpose High Level Programming Language.

Python is Robust(powerful and fast)
Plays well with others;
Runs everywhere(platfrom independent means runs in windows,linux,mac);
Easy to learn(especially easy syntax);
It is Opensource .

Powerful and Fast:Python handles large-scale data processing efficiently,used in data science,data analaysis ,AI and Machine learing

Plays Well with Others:

Used to develop
• Web Applications.
• Desktop Applications.
• Database (DB) Applications.
• Network Programming.
• Game Development.
• Internet of Things (IoT).

Python will combine with other programming language

• CPython (Python with C).
• JPython / Jython (Python with Java).
• IronPython (Python with C# / .NET).
• PyPy(Powerful python).
• RubyPython.

Python filename extension: .py

Python runs everywhere
- Runs in windows,linux,mac ..

Diff b/t High-Level Programming Languages & Low-Level Programming Languages :

1. High-Level Programming Languages:
It is easy to understand by humans .written the code in english language .Eg:python,java,c#,c++,javascript.

2. Low-Level Programming Languages:
It is understand only by machines and difficult to understand by humans like assembly or binary (0110,1011).

History of Python

Dutch programmer Guido van Rossum Discover Python in December 1989 at Centrum Wiskunde & Informatica (CWI) in the Netherlands

Python 0.9 - February 1991
Python 1.0 - January 1994

Python 2.0 - October 2000

Python 3.0 - December 2008

In Python 3.0 -> It broke backward compatibility.
Eg: if we write python 3.0 code and it can't used in python 2.0.

Diff b/t Programming language and scripting language

Programming language- language which do compilation(execute as whole file)
Scripting language-language which do interpretation(execute as line by line code)
Python is both Programming language and scripting language

Performance & Speedwise languages
1)c
2)c++
3)java
4)javascript
5)php
6)python

Static vs. Dynamic Typing language

Static Typed Language - it will check data type of the variable .Eg :C, C++, Java, and C#,Typescript.

// Java (Statically Typed)
int score = 100;      // 'score' is strictly an integer (number)
score = "High";       // ERROR! Caught immediately before the program runs

Dynamically Typed Language - it will not check for datatypes of the variable .Eg :Python,Javascript,PHP .

# Python (Dynamically Typed)
score = 100           # 'score' acts as an integer
score = "High"        # ALLOWED! 'score' is now text

Advantages of Python

1)Python is simple
2) Python is Open.
3) Python is interpreted language
4) Python is Extensible: [CPython / JPython / PyPy]
5) High Level Programming Language
6) Platform Indepedent.
7) Dynamically Typed Language

Disadvantages of Python

1) Performance is low compare to c,c++,java .its basically due to memory consumption is high in python
2) can't be used in Mobile App Developments
3) Runtime error due to its dynamically typed.

moving ahead ....

DEV Community: gobi2023

Identifiers,variables,Reserved words.

Starting Python.....