Python Tutorial - Learn Python Basics

Introduction to Python

• Python is an interpreted, high-level, general-purpose, dynamically typed programming language.

• It is also object-oriented, modular, and a scripting language.

• In Python, everything is considered an object.

• A Python file has an extension of .py.

• Python uses indentation to separate code blocks instead of curly brackets {}.

• We can run a Python file using the following command in cmd (Windows) or shell (macOS/Linux):

  $ python <filename.py> or $ python3 <filename.py>

Python does not require any imports to run a basic Python file.

Creating and Executing a Python Program

1. Open a terminal/cmd.
2. Create the program: nano > nameProgram.py or cat > nameProgram.py
3. Write the program and save it.
4. Run the program: python nameProgram.py

Basic Data Types

Data Type	Description
int	Integer values [0, 1, -2, 3]
float	Floating-point values [0.1, 4.532, -5.092]
str	Strings ["abc", "AbC", "A@B", "sd!", "`asa"]
bool	Boolean values [True, False]
complex	Complex numbers [2+3j, 4-1j]

Python Keywords

• As of Python 3.11, there are 36 keywords.

Keyword	Description	Category
True	Boolean value for true (or 1)	Value Keyword
False	Boolean value for false (or 0)	Value Keyword
None	Represents the absence of a value	Value Keyword
and	Logical AND (returns true if both operands are true)	Logical Operator
or	Logical OR (returns true if at least one operand is true)	Logical Operator
in	Membership operator (checks if a value is present in a sequence)	Membership Operator
is	Identity operator (checks if two variables refer to the same object)	Identity Operator
not	Logical NOT (inverts a boolean value)	Logical Operator
if	Starts a conditional statement	Conditional
elif	Used for additional conditions in an if statement	Conditional
else	Used in conditional statements for the default case	Conditional
for	Starts a for loop	Iteration
while	Starts a while loop	Iteration
break	Exits a loop prematurely	Iteration Control
continue	Skips the current iteration of a loop	Iteration Control
def	Defines a function	Structure
class	Defines a class	Structure
lambda	Creates an anonymous function	Structure
with	Used with context managers	Structure
as	Creates an alias	Structure
pass	A null operation (does nothing)	Structure
return	Returns a value from a function	Return
yield	Used in generator functions	Return
import	Imports modules	Import
from	Imports specific names from a module	Import
try	Starts a try...except block	Exception Handling
except	Handles exceptions	Exception Handling
finally	Code that always executes in a try...except block	Exception Handling
raise	Raises an exception	Exception Handling
assert	Used for debugging (raises an AssertionError if a condition is false)	Debugging
async	Used for asynchronous functions	Asynchronous Programming
await	Used within asynchronous functions	Asynchronous Programming
del	Deletes a variable	Variable Handling
global	Declares a global variable	Variable Handling
nonlocal	Declares a variable in an enclosing scope	Variable Handling

Python Operators

Operator	Description
( )	Parentheses (grouping, function calls, tuple creation)
[ ]	Brackets (list indexing, list slicing, list creation)
!	Logical NOT (inverts a boolean value)
~	Bitwise NOT (ones' complement)
-	Unary minus
+	Unary plus
*	Multiplication
/	Division
%	Modulo (remainder)
+	Addition
-	Subtraction
<<	Left bit shift
>>	Right bit shift
<	Less than
<=	Less than or equal to
>	Greater than
>=	Greater than or equal to
==	Equal to
!=	Not equal to
&	Bitwise AND
^	Bitwise XOR
|	Bitwise OR
and	Logical AND
or	Logical OR
=	Assignment
+=	Add and assign
-=	Subtract and assign
*=	Multiply and assign
/=	Divide and assign
%=	Modulo and assign
<<=	Left bit shift and assign
>>=	Right bit shift and assign
&=	Bitwise AND and assign
^=	Bitwise XOR and assign
|=	Bitwise OR and assign
,	Separator

Basic Data Structures

Lists

• A list is an ordered, mutable (changeable) collection that allows duplicate elements.

• Lists are created using square brackets:

thislist = ["apple", "banana", "cherry"]

• List items are ordered, mutable, and allow duplicate values.
• List items are indexed, starting from 0.
• The len() function returns the number of items in a list.
• Lists can contain different data types.

list1 = ["abc", 34, True, 40, "male"]

• The list() constructor can also be used to create a list.

thislist = list(("apple", "banana", "cherry"))

• The pop() method removes and returns the last item by default, or the item at a specified index.

thislist = ["apple", "banana", "cherry"]
print(thislist.pop())  # Output: cherry
print(thislist.pop(0)) # Output: apple

Tuples

• A tuple is an ordered, immutable (unchangeable) collection that allows duplicate elements.
• Tuples are created using parentheses.

thistuple = ("apple", "banana", "cherry")

• Tuple items are ordered, immutable, and allow duplicate values.
• Tuple items are indexed, starting from 0.
• The len() function returns the number of items in a tuple.
• To create a tuple with one item, add a comma after the item.

thistuple = ("apple",)
print(type(thistuple)) # Output: <class 'tuple'>

thistuple = ("apple")
print(type(thistuple)) # Output: <class 'str'>

• The tuple() constructor can also be used to create a tuple.

thistuple = tuple(("apple", "banana", "cherry"))

Sets

• A set is an unordered, mutable collection that does not allow duplicate elements.
• Sets are created using curly braces.

thisset = {"apple", "banana", "cherry"}

• Set items are unordered, unchangeable (but the set itself is mutable), and do not allow duplicate values.
• The len() method returns the number of items in a set.
• Sets can contain different data types.

set1 = {"apple", "banana", "cherry"}
set2 = {1, 5, 7, 9, 3}
set3 = {True, False, False}
set4 = {"abc", 34, True, 40, "male"}

• The set() constructor can also be used to create a set.

thisset = set(("apple", "banana", "cherry"))

• A frozenset() is an immutable version of a set.

set1 = {"apple", "banana", "cherry"}
frzset = frozenset(set1)
print(frzset)

Dictionaries

• A dictionary is an unordered, mutable collection of key-value pairs.
• Dictionaries are created using curly braces.

thisdict = {
  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}

• Dictionary items are accessed by key name.

print(thisdict["brand"]) # Output: Ford

• Dictionaries are mutable.
• Dictionaries cannot have two items with the same key.
• The len() function returns the number of items in a dictionary.
• Dictionary values can be of any data type.

thisdict = {
  "brand": "Ford",
  "electric": False,
  "year": 1964,
  "colors": ["red", "white", "blue"]
}

• The pop() method removes and returns the item with the specified key.

car = {
    "brand": "Ford",
    "model": "Mustang",
    "year": 1964
  }
x = car.pop("model")
print(x) # Output: Mustang
print(car) # Output: {'brand': 'Ford', 'year': 1964}

Conditional Branching

if condition:
    pass
elif condition2:
    pass
else:
    pass

Loops

Python has two main loop types: while loops and for loops.

While Loops

• A while loop executes a block of code as long as a condition is true.

i = 1
while i < 6:
  print(i)
  i += 1

• break exits the loop.
• continue skips the current iteration.
• else executes if the loop completes normally (without break).

For Loops

• A for loop iterates over a sequence (list, tuple, string, etc.).

fruits = ["apple", "banana", "cherry"]
for x in fruits:
  print(x)

• range() generates a sequence of numbers.
• Nested loops are loops within loops.
• else executes after the loop completes normally.
• A for loop cannot be empty, use pass if needed.

for x in [0, 1, 2]:
  pass

Function Definition

def function_name():
    return

Function Call

function_name()

• Return types are not explicitly specified.
• Functions return None by default.
• Any data type can be returned.