INTRODUCTION

What is Python?

Python is the fastest-growing programming language. It consistently ranks among the top 3 on surveys.

There are others programming languages like Java and C++.

Python is a general-purpose, high-level interpreted language with easy syntax and dynamic semantics.

It was developed by Guido Van Russum in 1989

Who uses Python?

What is Python used for?

1. Create websites because it has libraries for internet protocols like HTML  and XML, JSON, email processing, FTP, IMAP.
2. Desktop GUIs app development using inbuilt modules such as Tkinter as  well as web applications using third party libraries such as Django, Flask
3. Science and Numeric applications with the use of Scipy, Pandas, IPython,  Numpy
4. Software development: software developers make use of Python as a  support language. Scons, Buildbot, Apache Gump, Roundup, Trac
5. Games and 3D graphics
6. Data analysis, Artificial intelligence and Machine Learning
7. Database access

Why use Python?

• It works on different platforms such as Windows or Mac, or even Linux, Raspberry Pi

• The syntax is close to English language and contains no semicolons or curly brackets. Compare the two ways of printing a simple statement using C++ and Python as shown below. Which is easier?

• Developers like Python because they achieve same results as other languages but with fewer lines of code

How do you use Python?

To begin coding in python, download the software from www.python.org

OPERATORS

Arithmetic Operators

Maths	Python
2 + 3 = 5	2 + 3
5 x 6	5 * 6
17 / 6	17 / 6
quotient of 17 / 3	17 // 3
remainder of 17 / 3	17 % 3

divmod (24, 6) will return (4, 0), that is, the quotient and the remainder.  It is similar to (a//b, a % b)

# Code to show operators  

a = 2 + 3

print (“The sum of 2 and 3 is”, a)  

b = 5 * 6

print (“The product of 5 and 6 is”, b)  

c = 17/6

print (“The result of 17 divided by 6 is”, c)

d = 17//3

print (“The quotient when 17 divides 3 is”, d)  

e = 17 % 3

print (“The remainder when 17 divides 3 is”, e)

Assignment Operators

a = 3 assign or equate 3 to a  

a += 3 add and assign to a  

a -= 3 subtract and assign to  

a *= 3 multiply and assign to  

a /= 3 divide and assign to

a %= 3 get the remainder and assign to a

# Assignment Operators  

a = 2

print (“Initial value of a is”, a)

a += 3

print (“After adding 3, we get”, a)

a -= 3

print (“After subtracting 3, we get”, a)

a *= 3

print (“After multiplying by 3, we get”, a)

Comparison Operators

> is greater than

< is less than

== is equal to

!= is not equal to

>= greater than or equal to

<= less than or equal to

# Comparison Operators  

x = 2

y = 3

print (“Is y greater than x?”, y > x) 

print (“Is x greater than y?”, x > y)  

print (“Are x and y equal?”, x == y)

# Comparison Operators  

p = 25

q = 50/2  

r = 5**2

print (“Are p and q equal?”, p == q)

print (“Perhaps q is not equal to r:”, q != r)

print (“I believe p is greater than or equal to r:”, p >= r)

Logical Operators: and/or/not

OR operator

AND Operator

NOT Operator

Logical operators are usually used with conditional statements

# logical operators

# They are usually used with conditional statements  p = 2

q = 7

print (“Is p greater than 1 AND less than 5?”, p > 1 and  p < 5)

print (“Is q greater than 4 OR less than 2?”, q > 4 or q < 2)

Absolute and Boolean Operators

abs means

absolute value abs (-43) = 43

bool (0) and bool (none) returns False. All others return True

Membership operators: in / not in

They are used to check if an element belongs to a given set. 

The values returned are True or False

# membership operators

fruits = [“apple”, “banana”, “carrot”]

print (“Is banana in fruits?”, “banana” in fruits) 

print(“Is mango in fruits?”, “mango” in fruits)

DATA TYPES

• Numbers: integer, float, complex

• Boolean

• String

• List

• Tuples

• Dictionaries

• Sets

STRINGS

They are enclosed in a single or double quotes.  a = “Python”

Strings can be counted, with the first character having index = 0.

Length = 6

# strings

a = “Python”

b = “Hello, World!”

print (“The first character in string a is:”,a[0])  

print (“The last character in string ais:”, a[-1])

print (“The number of characters in string a is:” ,len(a))

We use square brackets to slice strings

str[index]

str[start : stop]: returns the string between the startindex and stop index

str[start : stop : step]: returns the string between the start and stop index in  steps

# strings

c = “iPrep Educational”

print (“The string between the 2nd and 8th characteris:”, c[2:8])

print (“The string btw the 3rd & 15th character skipping one is:”, c[3 : 15: 2])

print (“The string from beginning to the 7th character is:”, c[:7])

print (“The string from the 4th character to the end is:”, c[4:])

print (“The string btw the 5th & the 3rd to the last character is:”, c[5:-3])

i	P	r	e	p		E	d	u	c	a	t	i	o	n	a	l
0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16

Strings

str.capitalize() returns the string with the first character of the first word capitalized and the rest in lower case

str.replace (“string”, “replacement”) will replace a string with another string

str.casefold() /str.lower() returns the string in lowercase

str.title() returns the string where each word begins with a capital letter  str.upper() returns the string where each word is in uppercase

str.swapcase() returns a copy of the string with uppercase characters converted to lowercase and vice versa

#strings

d = “This is a Python Tutorial”

print (“First letter capitalized and others in lowercase:”, d.capitalize())

 print (“Replacing letter ‘a’ with ‘the best’:”, d.replace(‘a ’, ‘the best ’))

#notice the space after the ‘a’ to avoid affectingthe ‘a’ in Tutorial  print (“In lowercase:”, d.lower())

print (“in uppercase:”, d.upper())

print (“lower case and uppercase swapped:”,d.swapcase())

str.format() will perform a formatting operation on replacement fields delimited by {}.

Each replacement field contains either the numeric index of a positional argument or the name of a keyword argument

“The sum of 1 + 2 is {0}”.format (1+2)

str.format(age) will insert the age andreturn result as a string  str = “Dipo is{age} years old” *show these codes*

Multiple formating is allowed

qty = 8

price = 500

myorder = “I want {}pieces of items for {}”  print (myorder.format(qty, price)

# strings

e = “John is {} years old while Kelly is {}”

f  = “John is {age_J} years old while Kelly is{age_K}”

print (e.format(2, 10))

print (f.format (age_J = 2, age_K = 10))

We can count the number of  times a character appears in a string within a given a range

“James is too good”.count(“o”) returns 5  “James is too good”.count (“o”, 1,15) returns 3

We can also find the position of  the first time a given character appears in  a string by using the .find() or.index() methods

“James is too good”.find(“o”, 0, 20) returns 10

If  we want to split the words in a string, we use the.split() and use sep as the delimeter string

“James is too good”.split(sep = “ ”) returns [“James”,“is”, “too”, “good”]

Working backwards, we can use the “seperator”.join(iterable)” to convert a list to a string and puts the separator string in between the items

“ ”.join([“James”, “is”, “too”, “good”]) will return “James is too good”

str.strip() removes whitespace before and after the string or whatever is specified in the bracket

“  removes whitespace  ”.strip() will return ‘removeswhitespace’

# The % operator in a string object

print (“%(language)s has %(number)03d quote types”

%{“language” : “Python”, “number” : 2})

LISTS

The list is probably the most versatile datatype in Python.  Characteristics

• Ordered: they can be indexed

• Mutable: the elements can be modified after it is created

• Homogenous (or heterogenous) data: they can contain numbers, strings,  or even another list

• Allows duplicate

List may be thought of like a plate rack. They can be created using

[ ], list (iterable), [x for x in range(10)]

#creating lists

fruits = [“apple”, “banana”, “carrot”]

print (fruits)  

a = [ ]

#empty list created

print (type(a)) 

#asking Python for the datatype of a

students = (“Ali”, “Benjamin”, “Casper”)

print(list(students))

b = [x for x in range (10)]  print (b)

Look at this list we created

L = [15, “Mike”, 23.75, [20, 40, 60]]

Length = 4

list.append (x): add an item to the end of a list equivalent to a[list(a):] = [x]  

list.extend (t): extends list with the contents of another list t

You can also add any iterable such as tuples, sets and dictionaries using this extend

list [i : j] = iterableT slice of list from i to j is replaced by the contents of the  iterable T

#list methods

fruits = [“apple”, “pawpaw”, “banana”, “orange”, “mango”, “banana”]

print (“The number of items in thelist is:”, len(fruits)) 

print (“The item in the third position is:”, fruits [2])

 print (“The first 3 items are:”,fruits[ : 3])

print (“How many times can we find banana?”,fruits.count(‘banana’))

You can change the items in a list by referring to a range

fruits[2:3] = [‘apple’, ‘pawpaw’, ‘orange’, ‘pineapple’] will insert the new list in the third position

fruits[2:3] = ‘mango’ will put it as [‘apple’, ‘pawpaw’, ‘orange’, ‘m’,’a’,’n’,’g’,’o’,  ‘pineapple’]

list.insert (i, x): insert an item in a given position. Thei is the position of the element before which to insert

list.remove (x): remove the first item from the list whose value is x. 

list.copy(): creates ashallow copy of list. newList =oldList.copy()

list.pop(i): remove the item from the list and return it. Ifno index is specified, it  removes the last item

list.clear () empties the list. The list still remains but has no contents

#list methods

fruits = [“apple”, “pawpaw”, “banana”, “orange”, “mango”, “banana”]  

#let’s add grape to the fruits

fruits.append (‘grape’) 

print(fruits)

#Then let’s insert lemon between the pawpaw and banana 

fruits.insert (2, ‘lemon’)

print (fruits)

#Why don’t we take out mango 

fruits.remove (‘mango’)

print (fruits)

#make a copy of the list of fruits 

new_fruits = fruits.copy()

print (new_fruits)

#And then let’s clear the old list 

fruits.clear()

print (fruits)

#list methods

students_A = [‘Mike’,‘Helen’, ‘David’]  

students_B = [‘Stacy’,‘Henry’, ‘Paul’]

students_A.extend(students_B) 

#adding one list to another 

print (students_A)

students_A [1:1] = students_B 

#adding one list to another by index 

print (students_A)

#list methods

fruits = [‘orange’, ‘banana’, ‘pawpaw’, ‘apple’] 

numbers = [4, 15, -3, 7]

fruits.sort() #arranges the fruits alphabetically

numbers.sort() #arranges the numbers in ascending order 

print (fruits)

print (numbers)

The .sort() method can take two arguments – key and reverse  

fruits.sort(key = None, reverse = True)

You can also reverse a list using .reverse()

del listName[0] will remove the first item but del listName will delete the list entirely

list.index (x[, start[, end]]) index of the first occurence of x in list (at or after start index and before end index

list.count (x) total number of occurences of x in list  list.sort(key = none, reverse = False)

e.g. numbers = [2, 6, 3, 18]

numbers.sort(reverse = True) will give 18, 6, 3, 2

e.g2

def myfunc(n):  

return abs(n)

numbers = [100, 50, 65, 82, 23]

numbers.sort(key = myfunc)  print(numbers)

RESULT: [50, 65, 23, 82, 100]

By default, the listName.sort() is case sensitive, that is, it will sort out items that  begin will a capital letter before items in small case. if you want it to be case  insensitive, use the key = str.lower

list.reverse (): reverses the items of  list in place

list comprehension consists of brackets containing an expression followed by a ‘for’ clause, then zero or more for or if clauses

fruits = [‘apple’, ‘banana’, ‘pawpaw’]

[print (x) for x in fruits]

[(x, y) for x in [1, 2, 3] for y in [3, 1, 4] if  x!=y]

newlist = [expression FOR item IN iterable IF condition == True]

TUPLES

• They are immutable: You cannot change them but only redefine them.

• They do not support item assignment

•T hey are usually used to store heterogenous data

VarName = (‘item1’, 31, ‘item2’) 

They can be constructed using ( ), (a, b, c), tuple(iterable)

Tuples don’t have the inbuilt .append( ) function. However, if you want to add items to a tuple, you can

1. convert it to a list, add, and convert back to tuple

2. add tuple to tuple 

unpacking a tuple

fruits = (‘apple’, ‘orange’, ‘cherry’) 

(green, yellow, red) = fruits

DICTIONARY

Dictionaries are ordered, changeable datatypes that do not allow duplicates

Ordered means the items have a defined order and can be referenced by an index.

car = {‘brand’ :‘Toyota’, ‘model’ : ‘Corolla’}  Notice the use of curly braces

{key: value} makes an item

So you can construct a dictionary using {key : value} like the example  above, or

car = dict([(‘brand’, ‘Toyota’), (‘model’,‘Corolla’)])

car[‘colour’] = ‘black’ will add a new item to the dictionary

.items() will return each item in a dictionary as a list

Use DictName.update (DictName2) to add items to a dictionary

car.pop (‘model’) will remove the item specified by the key  car.popitem() removes the last item

VarName = {‘Var1’:15, ‘Var2’:20}. DictName.values(), DictName.keys (),  Using for loop will return just the keys

for x in car:

print (x)

for x, y in car, items():

This will loop through keys and values

print (x, y)

for b in car:

print (car[x]) will return values

#dictionary methods

car_1 = {‘brand’: ‘Toyota’, ‘model’: ‘Corolla’}

car_2 = {‘brand’: ‘Kia’, ‘model’: ‘Rio’}  

#let’sretrieve the model of  car_1

print (car_1[‘model’])

#let’s add another key-value pair to car_1 

 car_1[‘year’] = 2015

print (car_1)

#how do we get the items  

print (car_1.items())

#Let’s get the keys and values separately 

print(car_1.keys())

print (car_1.values())

Nested Dictionaries

myFamily = {‘child’: {‘name’: ‘dipo’, ‘year’: 2005},‘child2’:{‘name’: ‘Akin’,  ‘year’: 1983} }

SETS

A set in Python is

• an unordered collection, which means you can’tindex them

• unique with no duplicate elements.

• changeable.

Sets can be used to test for membership and removing duplicates

Curly brackets {} or the set ( )function can be used to create sets.

#set methods

A = {‘blue’, ‘green’, ‘yellow’, ‘green’}  B = set (‘string’)

C = set ([3, 2, 6])

print (A)  

print (B)

print (C)

Did you notice the duplicate element was removed when it printed set A?

You can add an element to a set using .add( ). For example, A.add (‘purple’) will add  purple to the set A

#set methods

X = {2, 4, 6, 8, 10, 12, 14}

Y = {1, 2, 3, 6, 9, 18}

print (“The union of both sets is”, X | Y)

print (“Intersection (common elements) of both set is”, X & Y)

print (“Elements in X but not in Y are”, X – Y)

print (“Elements in X or Y but not in both include”, X ^ Y)

CONDITIONAL STATEMENTS

IF/ELSE Statements

These usual coding statements are used to make decisions only if a certain condition is satisfied

if test expression: 

statement(s)

comparison operators (>  <  >=  <=  ==  !=) are very often used with if/else statements.

A colon is added at the end of the if, elif  and else statements

Also, you will see that Python relies on indentation to define the scope of a code just the way other programming languages use curly brackets.

#if/else statements  

a = 33

b = 15

if a > b:

print (“a is greater than b”)

age = 16

if age >= 18:

print (“You are eligible to vote”)  else:

print (“You are not up to the required age to vote”)

You can combine multiple conditions using elif keyword

if test expression:

statement  

elif  test expression:

statement(s) 

else:

statement

#if/else statements  

movie_cost = 2000

age = int (input (“Enter your age: “))

if age <= 12:

print (“Discounted for children. Pay”, 3/5 * movie_cost)

elif age >= 60:

print (“Discounted for senior citizens. Pay”, 1/2 * movie_cost)

else:

print (“Pay”, movie_cost)

FOR – WHILE loops

while loop executes as long as the condition remains true

while condition:

statement(s)

#While loop  

x = 1

while x <= 5:

print (“Hello from the while loop”, x)

x += 1

print (“Goodbye from the while loop”)

For loops execute a sequence of statements multiple times depending on the iterable (range, list, string, tuple, dictionary):

#for loop

fruits = [‘apple’, ‘banana’, ‘pineapple’, ‘orange’]  

for k in fruits:

print (k, len(k))

Range Function

The range ( ) function generates an arithmetic progression

range (n)

range (start, stop, step)  

Note that the last number is never printed

Python Code	Output
for i in range(5): print (i)	0, 1, 2, 3, 4
for i in range (1, 7):   print (i)	1, 2, 3, 4, 5, 6
for i in range (1, 7, 2): print (i)	1, 3, 5

list (range(4)) gives you the values [0, 1, 2, 3]

sum (range(4)) finds the sum of the first 4 numbers starting from 0, and it gives 10

Loop Control Statements

break tells the machine to leave the loop enclosing for or while loop

continue goes on with the next iteration of the loop. It will bypass any code written under it

pass is like a filler statement – it doesn’t do anything

next (iterable, default)

default is an optional parameter. It is returned when there is no next item and the iterator is exhausted

#break, continue and pass

for attempt in range (1, 4):

attempts_remaining = 3 – attempt

password = input(“Enter your password: ”)

if password == “python”:

print (“Correct password \n unlocking your device”)

break

print (“incorrect password \n attempts remaining = ”, attempts_remaining)

With the ‘else’ statement in a while/for loop, we can continue with a block of  code once the condition is no longer true or when the loop has ended.

Nested loops

You can have a loop within a loop. The inner loop will be executed first before the outer loop

#break, continue and pass

a = int (input(“Enter the lower limit: ”))

b = int (input(“Enter the upper limit: ”))

for i in range (a, b):

for n in range (2, i):  

if i % n == 0:

break

else:

print (i, “is a prime number”)

try and except

The try block allows you to test a block of code for errors.  The except block lets you handle the error

They can be used to check the user hasn’t typed anything wrong.

while True:

try: x = int (input (“Enter number”))

break

except ValueError: print (“Oops. Incorrect”)

It may be used to check internet connection

The raise statement allows the programmer to force a specified exception to occur

#try and except

try:

print (a)

except:

print (“An error exception occurred for not defining a”)

FUNCTIONS

A function is a block of code that runs when it is called. The keyword def  introduces a function definition.

It must be followed by the function name and the list of  parameters in bracket, then a colon(:).

def  functionName (pos1, pos2, /, pos_or_kwd, *, kwd1, kwd2):

The parameter is the variable inside a function while an argument is the value sent to the function.

A function definition looks like

def  dog (Bingo, type = “Pitbull”):

A function must be called with the correct number of  arguments

You can have

• 2 positional arguments,
• positional & keyword argument,
• 2  keyword arguments

but you cannot have a positional argument after a keyword argument.

If  the number of  keywords are unknown, add * before the parameter  

def  name (*kids):

print (‘Hello’ + kids[2])  

name (‘Akin’, ‘Bayo’)

If you call a function without an argument, it uses the default value  (specified by the parameter).

A function can call itself (recursion)

Global and Local Variables

Variables that are created outside of a function are called global variables. Local variable cannot be called outside a function

To create a global variable inside a function, use the global keyword  

def  myfunc():

global x

x = fantastic

#global and local variables

x = “This is a global variable”  

def  check():

x = “This is a local variable”

print (x)

check()

Python Lambda Function

It is quick way to write a small, one-line function

lambda arguments:

expression

It may be used as an anonymous function inside another function  

inc = lambda a: a + 1

print (inc(1))

is equivalent to

def  inc(a):

return a+1

print (inc (1))

people = [‘Dr. Akin Fada’, ‘Dr. Lawal Oyene’, ‘Dr. Oke Onianwa’, ‘Dr. Dipo Daboiy’]  

def splitNames (person):

title = person.split()[0]

lastName = person.split()[-1]

return ‘{}{}’.format (title, lastName)  

list (map(splitNames, people))

def splitNames2(person):

return person.split()[0] + ” ” + person.split()[-1]  for person in people:

print (splitNames2(person) == (lambda x: x.split()[0] + ‘ ‘ + x.split()[-1](person))

CLASSES

A class is used to define the characteristics of an object (fields and properties) and the things it can do (methods).

It is collection of  methods and variables under a common name. Class  provide a means of  bundling data and functionality together.

A namespace is a mapping from names to objects

class ClassName:

statement1

statement2

Class objects supports two kinds of  operation: attributes references and  instantiation

An attribute may simply be any name following a dot. E.g.

z.real

real is an attribute of the object z.

often the first argument of a method is self

Class variables are for attributes and methods shared by all instances of the class

instance variables are unique to each instance.

An instance is the class object that is created at run time. It can be called the physical manifestation of a class. An instance is created when a class is assigned to a variable.

An object is the actual thing made using the blueprint (class) and the instance is the virtual copy of that object.

A method is a function that belongs to an object. A constructor (init) is a special type of method that Python calls when it creates an object/instance.

If  you create a class called student, you expect it to have related variables  like Serial_No, School, Age. Stock price, average rainfall will ruin the point  of  having a class.

Classes help with reusability. You can call the same methods defined in  another class

They also help with maintainability because you use less lines making it  easier to debug. You can make custom exceptions to your classes

Inheritance is the concept of  having a class inherit properties from  another class.

class Inheritance

class DerivedClassName (BaseClassName):

Encapsulation

This is the concept of  restricting the direct access of  variables and  methods. It only allows the object itself  to change its variable, just to avoid  any accidental change. We call such variables private or protected.

PROTECTED – can only be accessed by the class itself, or its sub-classes.  You declare a protected member by using a single underscore _ as preficx

PRIVATE – only accessed by the main class itself. You use a double underscore as prefix.

MODULES

Modules are libraries that hold functions, Python definitions and  statements.

It can contain executable statements

The file name is the module name with the suffix .py appended and saved  in the current directory.

To use a module, you need to import the contents

import module_name

Random module

import random

It provides tools for making random choices

random.sample / random.choice / random.randrange/random.random

Randint

Randbytes

Shuffle

uniform

math module

import math

sin/cos/tan/pi/radians/degree/log

Statistics

Mean/median/mode/quantiles, variance, correlation

Time, datetime

import time

os module

import os

This module allows us to use the functionalities of the operating system.

json module

Json stands for JavaScript Object Notation) is a lightweight data interchange format

import json

json.dumps (given_list or given_dict or given_tuple or given_string)

stands for dump string. This will modify a Python dictionary to a JSON string

Note that keys in key-value pairs of JSON are always of the type str.

json.load() accepts the file object, parses the JSON data, populates a Python dictionary with the data

json.loads(given_json) stands for load string. It takes in the file content and not the file path as a string and returns a Python dictionary

csv module

Comma Separated values format is the most common file type for spreadsheets and databases

import csv

with open(‘csv_name.csv’, newline =‘’) as variable_name:

  reader_name = csv.reader (variable_name, delimiter =‘’, quotechar = ‘|’))

  #for loop

with open(‘csv_name.csv’, ‘w’, newline =‘’) as variable_name:

  writer_name = csv.writer (variable_name, delimiter =‘’)

  writer_name.writerow(string)

DictReader: after reading the file,

  #for row in reader:

  print (row[‘first_name’], row[‘last_name’])

DictWriter : after writing

  columns_list = [column_names]

  writer = csv.DictWriter(csvfile, fieldnames = column_list)

  writer.writeheader()

  writer.writerow({‘first_name’: ‘James’, ‘last_name’: ‘Bond’})

turtle module

import turtle

tkinter module

import tkinter

Third Party Modules

pandas, numpy, matplotlib are commonly used packages for data analysis, manipulation and presentation

Django, flask are used to create websites and develop web software

Pygame is used to create video games

NLTK (Natural language tool kit) is used for processing language data

WHAT’S NEXT?

With Python you are equipped to gain understanding in

1. Data Science
2. Machine Learning
3. Deep Learning