x = 10
y = "Hello"

x = 5
y = 9
z = x + y
print(z)

x = 5
y = 'Hello'
print(type(x)) # prints <class 'int'> 
print(type(y)) # prints <class 'str'>

a = 3.14
b = int(a) # converts a to an integer 
c = str(a) # converts a to a string

x = 5
y = x*2

y = 5

if y > 0: print("Positive") 
elif y == 0: print("Zero") 
else: print("Negative")

if condition:
# do something
else:
# do something else

x = 10
if x > 0:
    print("x is positive")
else:
    print("x is negative or zero")

x = 10
if x > 0:
    print("x is positive")
elif x < 0:
    print("x is negative")
else:
    print("x is zero")

for item in sequence:
# do something with item

fruits = ["apple", "banana", "orange"]
for fruit in fruits:
    print(fruit)

range(start, stop, step)

for i in range(1, 11):
    print(i)

while condition:
# do something

n = 1
while n < 100:
    print(n)
    n = n * 2

for i in range(1, 11):
    if i == 5:
        break # exit from loop when i equals 5
    print(i)

for i in range(10):
    if i % 2 == 0: #if i is even 
        continue # skip this iteration
    print(i) # print only odd numbers

numbers = [1, -2, 3, -4, 5]
sum = 0 
for n in numbers: 
    if n < 0: # if n is negative
        continue # skip this iteration
    sum += n # add n to sum
print(sum) #prints 9

#Creating a list of numbers
numbers = [1, 2, 3, 4, 5]
print(numbers) # prints [1, 2, 3, 4, 5]

# Creating a list of strings
fruits = ["apple", "banana", "cherry"]
print(fruits) # prints ["apple", "banana", "cherry"]

# Creating a list of mixed types
mixed = [True, 3.14, "hello", None]
print(mixed) # prints [True, 3.14, "hello", None]

# Creating an empty list
empty = []
print(empty) # prints []

# Creating a list using the list() function
letters = list("abcde")
print(letters) # prints ["a", "b", "c", "d", "e"]

# Accessing items by index (zero-based)
numbers = [1 ,2 ,3 ,4 ,5]
print(numbers[0]) # prints 1
print(numbers[-1]) # 5

# Slicing a list (returns a new list)
numbers = [1 ,2 ,3 ,4 ,5]
print(numbers[1:3]) # prints [2 ,3]
print(numbers[:2]) # prints [1 ,2]
print(numbers[3:]) # prints [4 ,5]
print(numbers[:]) # prints [1 ,2 ,3 ,4 ,5]

# Changing items by index (mutating the list)
numbers = [1 ,2 ,3 ,4 ,5]
numbers[0] = 10
print(numbers) # prints [10 ,2 ,3 ,4 ,5]

my_tuple = (1, 2, 3)
print(my_tuple) #prints (1, 2, 3)

We can also create a tuple without using round brackets. This is called tuple packing. For example:

my_tuple = 1, 2, 3
print(my_tuple) #prints (1, 2, 3)

If we want to create a tuple with only one item, we need to add a comma after the item. Otherwise, Python will treat it as a regular value and not as a tuple. For example

my_tuple = (1,)
print(type(my_tuple))

<class 'tuple'>

my_tuple = (1)
print(type(my_tuple))

<class 'int'>

my_tuple = ("apple", "banana", "cherry")
print(my_tuple[0])
print(my_tuple[1])
print(my_tuple[2])

apple
banana
cherry

my_tuple = ("apple", "banana", "cherry")
print(my_tuple[-1])
print(my_tuple[-2])
print(my_tuple[-3])

cherry
apple
banana

my_tuple = ("apple", "banana", "cherry", "orange", "kiwi")
print(my_tuple[1:4]) # from index 1 (inclusive) to index 4 (exclusive)
print(my_tuple[:3]) # from index 0 (inclusive) by default to index 3 (exclusive)
print(my_tuple[2:]) # from index 2 (inclusive) to end by default
print(my_tuple[-4:-1]) # from index -4 (inclusive) to index -1 (exclusive)
print(my_tuple[::2]) # every second item from start (inclusive) by default)to end by default

('banana', 'cherry', 'orange')
('apple', 'banana', 'cherry')
('cherry', 'orange', 'kiwi')
('banana', 'cherry', 'orange')
('apple', 'cherry', 'kiwi')

my_tuple = ("red", "green", "blue")
for color in my_tuple:
    print(color.upper())

RED
GREEN
BLUE

# create an empty set
s = set()

# create a set with some integers
s = {1, 2, 3}

# create a set with mixed data types
s = {1.5, "hello", (4, 5)}

# create a set from a list
l = [1, 2 ,3 ,4 ,5]
s = set(l)

# create a set from a tuple
t = ("a", "b", "c")
s = set(t)

# create a list with duplicate elements
l = [1 ,2 ,3 ,4 ,5 ,1 ,2]

# create a set from the list
s = set(l)

# print the set
print(s) # prints {1 ,2 ,3 ,4 ,5}

my_dict = {"name": "Alice", "age": 25, "occupation": "programmer"}

my_dict = dict(name="Alice", age=25, occupation="programmer")

print(my_dict["name"]) # prints Alice 
print(my_dict["age"]) # prints 25

print(my_dict.get("name")) # prints Alice
print(my_dict.get("gender")) # prints None 
print(my_dict.get("gender", "female")) # prints female

my_dict["hobby"] = "reading" 
print(my_dict) # prints {'name': 'Alice', 'age': 25, 'occupation': 'programmer', 'hobby': 'reading'}

my_dict["age"] = 26 
print(my_dict) # prints {'name': 'Alice', 'age': 26, 'occupation': 'programmer', 'hobby': 'reading'}

my_dict.update({"name": "Bob", "city": "New York"}) 
print(my_dict) # prints {'name': 'Bob', 'age': 26, 'occupation': 'programmer', 'hobby': 'reading', 'city': 'New York'}

value = my_dict.pop("hobby") 
print(value) # prints reading print(my_dict) # prints {'name': 'Bob', 'age': 26, 'occupation': 'programmer', 'city': 'New York'}

value = my_dict.pop("gender", "unknown")
print(value) # prints unknown

def function_name(parameter1, parameter2,...):
# body of the function
# statements

function_name(argument1, argument2,...)

# Define a function that takes two numbers as input
#and returns their sum as output

def add(x,y):
    result = x + y # calculate the sum of x and y return result # return the sum as output
    return result

# Call the add function with 3 and 5 as arguments
sum = add(3,5) # store the returned value in sum variable

print(sum) # prints 8

import math
import numpy

math.sqrt(25) # returns 5.0
numpy.array([1, 2, 3]) # returns an array object

from math import pi
from numpy import random

random.randint(10) # returns a random integer between 0 and 9

from math import *
from numpy import *

try:
# code that may cause exception
except:
# code to run when exception occurs

try:
    x = 0
    y = 10 / x
    print(y)
except ZeroDivisionError:
    print("You cannot divide by zero")

try:
    a = int(input("Enter a number: "))
    b = 0
    c = a / 0
    print(y)
except ZeroDivisionError:
    print("You cannot divide by zero")
except ValueError:
    print("You must enter a valid number")

def square_root(x):
if x < 0:
    raise ValueError("Cannot take square root of negative number")
return x ** 0.5

print(square_root(4))
print(square_root(-1))

class NegativeNumberError(ValueError):
    pass

def square_root(x):
    if x < 0:
        raise NegativeNumberError("Cannot take square root of negative number")
    return math.sqrt(x)

# Open the file for reading only
file = open("example.txt", "r")

# Read all the data from the file
data = file.read()

# Print the data
print(data)

# Close the file
file.close()

This is an example text file.
It contains some sample data.
We can read it using Python.

# Open the file for reading only using a with statement
with open("example.txt", "r") as file:
# Read all the data from the file
data = file.read()

# Print the data
print(data)

# No need to close the file explicitly

# Open a text file in read mode
f = open("example.txt", "r")

#Read 10 characters from the current position

data = f.read(10) 
print(data)

#Read all remaining characters from the current position

data = f.read() 
print(data)

#Close the file

f.close()

Hello world! This is an example text file.

#Open a text file in read mode
f = open("example.txt", "r")

# Read one line and print it

line = f.readline() 
print(line)

#Read another line and print it

line = f.readline() 
print(line)

#Close the file

f.close()

Hello world!
This is an example text file.

#Open a text file in write mode (this will overwrite any existing content)

f = open("example.txt", "w")

#Write some data to the file

num_bytes = f.write("This is some new data.\n") 
print(num_bytes)

#Close the file

f.close()

19

#Open a text file in append mode (this will add new content at the end)

f = open("example.txt", "a")

#Write some lines to the file (note that we need to add \n for each line)

lines = ["This is another line.\n", "And one more.\n"] num_bytes = f.writelines(lines) print(num_bytes)

#Close the file

f.close()

import json

To read a JSON string or file into a Python object (such as a list or a dictionary), we can use the json.loads() function for strings or the json.load() function for files. For example:

# Read a JSON string into a Python object
json_string = '{"name": "Bob", "hobbies": ["reading", "gaming", "coding"]}'
python_object = json.loads(json_string)
print(python_object)
# Output: {'name': 'Bob', 'hobbies': ['reading', 'gaming', 'coding']}

# Read a JSON file into a Python object
with open("data.json") as f:
    python_object = json.load(f)
print(python_object)
# Output: {'name': 'Bob', 'hobbies': ['reading', 'gaming', 'coding']}

# Write a Python object into a JSON string
python_object = {'name': 'Bob', 'hobbies': ['reading', 'gaming', 'coding']}
json_string = json.dumps(python_object)
print(json_string)
# Output: {"name": "Bob", "hobbies": ["reading", "gaming", "coding"]}

# Write a Python object into a JSON file
with open("data.json", "w") as f:
json.dump(python_object, f)