Practical 0

Practical 0#

Goals#

  • Understanding fundamentals of Python programming:

  • Variables, data types, lists, sets and tuples.

  • Conditional expressions and loops

  • Sort

  • Dictionary

  • Files and user interaction

Exercise 1#

1. Comments

# This is a comment
print("Bonjour")

2. Variables

# a variable
message = "le monde!"
print(message)

a = 10
b = 20
c = a + b
print(c)

# floating point numbers
pi = 3.14
print(pi)

# data types
message1 = "Bonjour"
a = 12
pi = 3.14
print(type(message1))
print(type(a))
print(type(pi))

3. Concatenation of two strings

# concatenation of two strings
message = "le monde!"
print("Bonjour" + message)

# concatenation of two strings
message1 = "Bonjour "
message2 = "le monde!"
print(message1 + message2)

# concatenation involving two variables of different data types
# operation + on two different data types

# Uncomment the print statement and run the code
message1 = "Bonjour en Python"
a = 3
# print(message1 + a)

Why did you get this error? In the following code, we correct this error.

# concatenation solution involving two variables of different data types
message1 = "Bonjour en Python "
a = 3
print(message1 + str(a))

4. Lists

a = [10, 20, 30, 40, 50]
print(a)

a = [10, 20, 30, 40, 50]
print(a[0])
print(a[1])
print(a[2])
print(a[3])
print(a[4])

# Uncomment the print statement and run the code
a = [10, 20, 30, 40, 50]
# print(a[8])

Why did you get this error? We are trying to access a element at an index that does not exist.

message1 = "Bonjour en Python "
print(message1[0])
print(message1[1])
print(message1[2])
print(message1[3])
print(message1[4])
print(message1[5])
print(message1[6])
print(message1[7])

The above code displayed the individual characters in the string (or list of characters). We will now get the length of this string.

message1 = "Bonjour en Python "
print(len(message1))

Nous allons maintenant créer une liste d’entiers.

a = [10, 20, 30, 40, 50]
print(len(a))

a = [10, 20, 30, 40, 50]

# add a new number at the end of the list
a.append(60)
print(a)

a = [10, 20, 30, 40, 50]

# modify a number at a particular index
a[0] = 0
print(a)

Why did we get this error? We are modifying an element at a non-existing index.

# Uncomment the assignment statement and run the code
a = [10, 20, 30, 40, 50]
# a[6] = 20
print(a)

a = [10, 20, 30, 40, 50]

# inserting an element at a particular index will modify the list
a.insert(0, 0)
print(a)
print(len(a))

a = [10, 20, 30, 40, 50]
a.insert(6, 60)
print(a)
print(len(a))

a = [10, 20, 30, 40, 50]

# We will now try to insert a number at an index greater than the length
# of the list. We will see that we do not get any error and the new number
# is added at the end of the list
a.insert(10, 60)
print(a)
print(len(a))

5. Tuples (non-modifiable lists)

a = (10, 20, 30, 40, 50)
print(a)

a = (10, 20, 30, 40, 50)
print(a[0])

a = (10, 20, 30, 40, 50)

# We now try to modify a tuple
# Uncomment the code below and run the code
# A tupe is a non-modifiable list

# a[0] = 0
print(a)

6. Sets

# A set is a collection of distinct elements
a = {10, 20, 30, 40, 50, 10, 20, 30, 40, 50}
print(a)

a = {10, 20, 30, 40, 50, 10, 20, 30, 40, 50}
a.add(10)
print(a)

a = {10, 20, 30, 40, 50, 10, 20, 30, 40, 50}
a.add(60)
print(a)

a = {10, 20, 30, 40, 50, 10, 20, 30, 40, 50}
a.remove(40)
print(a)

We will now try different data types with the numbers and print the result

# set
a = {10, 20, 30, 40, 50, 10, 20, 30, 40, 50}
print(a)
print(type(a))

# tuple
b = (10, 20, 30, 40, 50, 10, 20, 30, 40, 50)
print(b)
print(type(b))

# list
c = [10, 20, 30, 40, 50, 10, 20, 30, 40, 50]
print(c)
print(type(c))

Exercise 2#

1. Conditional Expressions

a = 12
if a % 2 == 0:
    print(a, " is divisible by 2")
else:
    print(a, " is not divisible by 2")

lang = "Français"
if lang == "Français":
    print("Bonjour le monde!")
else:
    print("Hello World!")

2. Loops

Loops can also be used to access the elements at different indices.

for i in [10, 20, 30, 40, 50, 10, 20, 30, 40, 50]:
    print(i)

for i in (10, 20, 30, 40, 50, 10, 20, 30, 40, 50):
    print(i)

for i in {10, 20, 30, 40, 50, 10, 20, 30, 40, 50}:
    print(i)

2. Range

for i in range(0, 10):
    print(i)

for i in range(0, 10, 2):
    print(i)

# print() by default displays the message followed by a new line
# But you can change its behaviour
for i in range(0, 10, 2):
    print(i, end=" ")

for i in range(10, 0, -2):
    print(i)

for i in range(10, 0):
    print(i)

split(): the function can be used to separate a string using a specified delimited. By default, the delimiter is a white space.

for i in "Bonjour,le,monde!".split():
    print(i)

for i in "Bonjour,le,monde!".split(","):
    print(i)

Write a program in Python to display the following output

1

12

123

1234

12345

123456

1234567

12345678

Exercise 3#

1. Sort

num = [10, 20, 30, 40, 50, 10, 20, 30, 40, 50]
num.sort()
print(num)

2. Sort (decreasing order)

num = [10, 20, 30, 40, 50, 10, 20, 30, 40, 50]
num.sort(reverse=True)
print(num)

3. minimum

num = [10, 20, 30, 40, 50, 10, 20, 30, 40, 50]
print(min(num))

4. maximum

num = [10, 20, 30, 40, 50, 10, 20, 30, 40, 50]
print(max(num))

5. sorted()

You can use the function if you do not wish to modify your initial list by sorting.

num = [70, 20, 30, 10, 50, 60, 20, 80, 70, 50]
sortednum = sorted(num, reverse=True)
print(num)
print(sortednum)

Modify the code given below to display the five greatest unique numbers.

num = [70, 20, 30, 10, 50, 60, 20, 80, 70, 50]

# select first five numbers
sortednum = sorted(num, reverse=True)[:5]
print(sortednum)

We can also use the function for strings.

print(sorted("Bonjour le monde!".split(), key=str.lower, reverse=True))

Exercise 4#

1. Dictionary

a = {"contente": 12, "content": 12, "triste": 2}
print(a)
print(type(a))

a = {"contente": 12, "content": 12, "triste": 2}
for key in a:
    print("The word ", key, " apparait ", a[key], " fois")

a = {"contente": 12, "content": 12, "triste": 2}
for key, value in a.items():
    print("The word ", key, " apparait ", value, " fois")

a = {"contente": 12, "content": 12, "triste": 2}
a["joie"] = 10
print(a)

a = {"contente": 12, "content": 12, "triste": 2}
del a["triste"]
print(a)

mots = {"contente": 12, "content": 12, "triste": 2, "joie": 10}
print(sorted(mots))

mots = {"contente": 12, "content": 12, "triste": 2, "joie": 10}
mots_tuple = [(key, value) for key, value in mots.items()]
print(mots_tuple)

2. itemgetter

from operator import itemgetter

mots = {"contente": 12, "content": 12, "triste": 2, "joie": 10}
mots_tuple = [(key, value) for key, value in mots.items()]
print(sorted(mots_tuple, key=itemgetter(1)))

3. Interaction with user

# nom = input("Quel est votre nom?")
# print(nom)

# age = input("Quel est votre âge? ")
# print(age)
# print(type(age))

# age = input("Quel est votre âge? ")
# age = int(age)
# print(age)
# print(type(age))

Question: Write a program in Python that interacts with the user to obtain the following information of 5 students:

  • Name of student

  • Age

  • Grades in 5 modules

Once the information for all the five students is obtained, calculate and display the following values for every module:

  • average grade

  • maximum grade

  • minimum grade

Exercise 5#

1. Files

message = "Bonjour le monde"
with open("bonjour.txt", "w") as file:
    file.write(message)
file.close()

with open("bonjour.txt", "r") as file:
    text = file.read()
    print(text)
file.close()

message1 = "Bonjour le monde"
message2 = "Programmation en Python"
with open("bonjour.txt", "w") as file:
    file.write(message1)
    file.write(message2)
file.close()

with open("bonjour.txt", "r") as file:
    text = file.read()
    print(text)
file.close()

message1 = "Bonjour le monde\n"
message2 = "Programmation en Python"
with open("bonjour.txt", "w") as file:
    file.write(message1)
    file.write(message2)
file.close()

with open("bonjour.txt", "r") as file:
    text = file.read()
    print(text)
file.close()

2. readline()

This function can be used to read a file line by line and not the complete content in a single call like read()

message1 = "Bonjour le monde\n"
message2 = "Programmation en Python"
with open("bonjour.txt", "w") as file:
    file.write(message1)
    file.write(message2)
file.close()

with open("bonjour.txt", "r") as file:
    text = file.readline()
    print(text)
file.close()

message1 = "Bonjour le monde\n"
message2 = "Programmation en Python\n"
with open("bonjour.txt", "w") as file:
    file.write(message1)
    file.write(message2)
file.close()

with open("bonjour.txt", "r") as file:
    for line in file:
        print(line)
file.close()

Question: Copy any HTML file in your home directory. Write a program in Python to get the following values:

  • number of characters in the HTML file

  • number of lines in the HTML file

  • number of words in the HTML file

  • first twenty words in the HTML file

  • distinct words in the HTML file

Question: Copy the CSV file population.csv from the data folder. The file contains the population values between 1901 and 2016. Write a program in Python to get the maximum value.

  • the maximum value of population

  • the minimum value of population

Numpy#

import numpy as np

Matrix operations#

a1 = [1, 2, 3, 4]
b1 = [5, 6, 7, 8]

c1 = np.add(a1, b1)
print(c1)

c1 = np.subtract(a1, b1)
print(c1)

c1 = np.multiply(a1, b1)
print(c1)

c1 = np.multiply(4, b1)
print(c1)

c1 = np.dot(a1, b1)
print(c1)

c1 = np.dot(5, b1)
print(c1)

b1 = [5, 6, 7, 8]
c1 = np.dot(a1, b1)
print(c1)

a1 = [1, 2]
moyen = np.average(a1)
print(moyen)

Matrix Transposition#

b1 = [[5, 6, 7, 8, 9], [1, 2, 3, 4, 5]]
print(b1)
b1 = np.array(b1)
print(b1.T)

Split a matrix to two, horizontally and vertically#

a = [[0, 0, 0], [0, 1, 0], [1, 0, 0], [1, 1, 1]]
a = np.array(a)

a = np.hsplit(a, [2])

a1 = a[0]
a2 = a[1]
print(a1)
print(a2)

a = [[0, 0, 0], [0, 1, 0], [1, 0, 0], [1, 1, 1]]
a = np.array(a)

a = np.vsplit(a, [2])

a1 = a[0]
a2 = a[1]
print(a1)
print(a2)

Operations on two-dimensional matrices#

a2 = [[1, 2, 3, 4], [1, 2, 3, 4]]
b2 = [[5, 6, 7, 8], [5, 6, 7, 8]]

c2 = np.add(a2, b2)
print(c2)

c2 = np.subtract(a2, b2)
print(c2)

c2 = np.multiply(a2, b2)
print(c2)

a2 = [[1, 2, 3, 4], [1, 2, 3, 4]]
a2 = np.array(a2)
b2 = [[5, 6, 7, 8], [5, 6, 7, 8]]
b2 = np.array(b2)
c2 = np.dot(a2, b2.T)
print(c2)

Change the shape of a matrix#

b2.reshape(4, 2)
print(b2)

Creation of a matrix with random numbers#

a = np.random.rand()
print(a)

a = np.random.rand(1)
print(a)

a = np.random.rand(2, 5)
print(a)

a = np.random.rand(2, 3, 3)
print(a)

a = np.zeros(1)
print(a)

a = np.zeros(1, dtype=int)
print(a)

a = np.zeros((2, 5), dtype=int)
print(a)

Some functions to work with lists#

a = [12, 13, 14, 15]
a_reverse = reversed(a)

for num in a_reverse:
    print(num)

days = ["dimanche", "lundi", "mardi", "mercredi", "jeudi", "vendredi"]
days_num = list(enumerate(days))
print(days_num)

days_num = list(enumerate(days, start=1))
print(days_num)

a1 = [1, 2, 3, 4]
b1 = [5, 6, 7, 8]

zipped = list(zip(a1, b1))
print(zipped)

a1 = [1, 2, 3, 4]
b1 = [5, 6, 7, 8]

ezipped = list(enumerate(zip(a1, b1)))
print(ezipped)
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