2.1 Keywords and Identifiers
What are Keywords
Keywords are reserved words in Python that have special meanings and cannot be used as variable names.
Examples: if, else, while, for, True, False, None
List of Python Keywords
Python provides a predefined set of keywords. You can view them using:
import keyword
print(keyword.kwlist)
What are Identifiers
Identifiers are names used to identify variables, functions, classes, etc.
Example:
name = "Pooja"
Here, name is an identifier.
Rules for Naming Identifiers
- Must start with a letter or underscore
_ - Cannot start with a number
- Cannot use keywords
- Can contain letters, numbers, and underscores
Best Practices
- Use meaningful names (
student_nameinstead ofs) - Follow snake_case naming convention
2.2 Variables and Constants
What is a Variable
A variable is used to store data in memory.
Example:
age = 20
Declaring and Assigning Variables
Python does not require explicit declaration.
x = 10
y = "Hello"
Multiple Assignments
a, b, c = 1, 2, 3
Naming Conventions
- Use lowercase letters
- Separate words using underscores
What are Constants
Constants are values that do not change during execution.
Defining Constants
Python does not have built-in constants, but conventionally:
PI = 3.14
2.3 Data Types Overview
Introduction to Data Types
Data types define the type of data stored in a variable.
Numeric Types
a = 10 # int
b = 3.14 # float
c = 2 + 3j # complex
Sequence Types
list_data = [1, 2, 3]
tuple_data = (1, 2, 3)
string_data = "Hello"
Set Type
set_data = {1, 2, 3}
Mapping Type
dict_data = {"name": "Pooja", "age": 20}
Boolean Type
is_active = True
Checking Data Types
print(type(a))
2.4 Type Casting
What is Type Casting
Type casting means converting one data type into another.
Implicit Type Conversion
Python automatically converts types:
x = 10
y = 2.5
z = x + y # result is float
Explicit Type Conversion
Manual conversion:
x = int("10")
y = float(5)
z = str(100)
Common Functions
int()float()str()
Practical Example
num = int(input("Enter a number: "))
print(num + 5)
2.5 Input and Output Functions
Taking Input
name = input("Enter your name: ")
Displaying Output
print("Hello", name)
Formatting Output
age = 20
print(f"Age is {age}")
Multiple Inputs
a, b = input("Enter two numbers: ").split()
Escape Characters
print("Hello\nWorld")
2.6 Comments and Documentation
What are Comments
Comments are used to explain code.
Single-line Comments
# This is a comment
Multi-line Comments
"""
This is a
multi-line comment
"""
Writing Good Comments
- Keep them clear and concise
- Explain why, not what
Docstrings
Used to document functions:
def add(a, b):
"""This function returns sum of two numbers"""
return a + b
Importance of Documentation
- Improves readability
- Helps other developers understand code
- Makes maintenance easier
Conclusion
Understanding Python basics is essential for any beginner starting their programming journey. Concepts like keywords, variables, data types, and input/output form the foundation of all Python programs. Mastering these topics will make it easier to learn advanced concepts such as loops, functions, and object-oriented programming.
Consistent practice with these basics will help learners gain confidence and improve problem-solving skills. This module acts as the first major step toward becoming proficient in Python programming.
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