Conditional Expression

n = 10
print("Greater than 5") if n > 5 else print("smaller than 5") 

# output: Greater than 5

if, elif, and else

n = 5
if n > 2:
    print("n is greater than 2")
elif n < 2:
    print("n is smaller than 2")
else:
    print("n = 2")
# output: n is greater than 2

Loops

Loops in Python.

For Loops

for loops emphasize over a collection of items, like as list or dict and run a block of code with every element from the collection.

for i in [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]:
print(i)
# Output:
0
1
2
3
4
5
6
7
8
9

Range Function

range function – range is a function that returns a series of numbers under an iterable structure, so it can be utilized in for loops:

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

#output:

0
1
2
3
4
5
6
7
8
9

gives precisely the same outcome as before. Note that 10 isn’t printed as the range function excludes the number entered (known as the last number), range function has 3 parameters:

range(x) # one parameter means last number will be x(excluded)
range(x, y) # two parameters means 1st number will be x(included), last number will be y(excluded)
range(x, y, z) # three parameters means x will be first number(included), y will be the last number(excluded) and z will be the steps to the next number.

for i in range(10, 20):
print(i)
# Output

10
11
12
13
14
15
16
17
18
19

for i in range(10, 30, 2):
print(i)

#output:

10
12
14
16
18
20
22
24
26
28

While Loop

A while loop will cause the loop statements to be executed until the loop condition is false. This code will execute the loop statements a sum of 10 times.

i = 0 # assigning value to a variable
while i 10: # giving the condition where to terminate the loop
print(i)
i = i + 2 # giving the condition to increase the value of i after every step

There are more operations of loops, We will comprehend those later, at the present time you need to grasp a lot before plunging into advance level loops.

Dictionary

A dictionary is a collection of a key value store. It permits you to store and recover elements by referring a key. As word references are referred by key, they have very quick lookup.

Key : The ideal key to lookup, Value : The value to set or return.

Creating a Dictionary

d = {'key': 'value'}
print(d)

#Output
{'key': 'value'}

# To create a dictionary and populating it with values
stock = {'eggs': 5, 'milk': 10, 'bread': 5}
print(stock)

#Output
{'eggs': 5, 'milk': 10, 'bread': 5}

# To create a dictionary and populating it with values
stock = {'eggs': 5, 'milk': 10, 'bread': 5}
print(stock)

#Output
{'eggs': 5, 'milk': 10, 'bread': 5}

Accessing values of dictionary

# To access by elements
print(stock['milk'])
print(stock['bread'])

#Output
10
7

# To access by keys
print(stock.keys())

#Output
dict_keys(['eggs', 'milk', 'bread'])

# To access by values
print(stock.values())

#Output
dict_values([5, 10, 7])

Merging Dictionaries

To merge dictionaries update() function is used-

# Merging Dictionaries
shop = {'stock': 100, 'staff': 2}
market = {'shops': 100, 'employees': 200}
marketshop = {}
marketshop.update(shop)
marketshop.update(market)
print(marketshop)

#Output
{'stock': 100, 'staff': 2, 'shops': 100, 'employees': 200}

Iterating over a Dictionary

for i in marketshop:
   print(i)

#Output
stock
staff
shops
employees
#By default loop works in keys of a dictionary.

To use loop in both keys and values-

for i in marketshop:
    print(i, marketshop[i])

#Output
stock 100
staff 2
shops 100
employees 200

Python List

The Python list is a general data structure generally utilized in python programs. They are both mutable and sequence data type that permits them to be indexed and sliced. The list can contain various kinds of objects , including other list objects.

Working with List

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

#Output
[10, 20, 30, 40, 50]

# to add a new element in the list append method is used
a.append(60)
a.append(70)
a.append(80)
print(a)

#Output
[10, 20, 30, 40, 50, 60, 70, 80]

# to append another list
b = [90, 100]
c = ['Aman', 'Kharwal']
a.append(c)
a.append(b)
print(a)

#Output
[10, 20, 30, 40, 50, 60, 70, 80, ['Aman', 'Kharwal'], [90, 100]]

# to add elements of one list to another list
a = [10, 20, 30, 40, 50]
print(a)
b = [60, 70]
a.extend(b)
print(a)

#Output
[10, 20, 30, 40, 50, 60, 70]

Insert Function

insert(index, value)- Inserts value just before the specified index. You must know that the index in programming starts from 0 and not 1.

#insert 0 at position 0
a.insert(0, 0)
print(a)

#Output
[0, 10, 20, 30, 40, 50, 60, 70]

# insert 15 at position 2
a.insert(2, 15)
print(a)

#Output
[0, 10, 15, 20, 30, 40, 50, 60, 70]

Pop function

pop(index)-It removes the item at index. With no argument it removes the last element of the list.

# removing 2nd element from list
a.pop(2)
print(a)

#Output
[0, 10, 15, 20, 30, 40, 50, 60, 70]
[0, 10, 20, 30, 40, 50, 60, 70]

# removing last element from list
a.pop()
print(a)

#Output
[0, 10, 20, 30, 40, 50, 60, 70]
[0, 10, 20, 30, 40, 50, 60]

Remove Function

remove(value)- removes the specified value. It do not work on the index, it works on the value.

# remove
a.remove(30)
print(a)

#Output
[0, 10, 20, 40, 50, 60]

Reverse Function

reverse()- Reverses the list.

# reverse
a.reverse()
print(a)

#Output
[60, 50, 40, 20, 10, 0]

Count Function

count(value)- Counts the number of occurrences of some value in the list.

# count
a = ["John", "Aman", "John", 23, "John"]
print(a.count("John"))

#Output
3

Creating a list with Range function

# range
a = list(range(10))
print(a)

#Output
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Accessing list values

Python lists are 0-indexed, and act like arrays in other languages

a = [10, 20, 30, 40, 50]
print(a[2])
print(a[0])
print(a[-1]) # gives last item

#Output
30
10
50

User Input

To get input from the user, we need to use the input function.

a = input("Enter your first name: ")
b = input ("Enter your last name: ")
print(a, b)

#Output
Enter your first name: Shakshi
Enter your last name: Tripathi
Shakshi Tripathi

To add two numbers by taking user input:

a = int(input("Enter first number: "))
b = int(input("Enter second number: "))
print(a + b)

#Output
Enter first number: 25
Enter second number: 20
45

I used int before the input in light of the fact that to add two integers we need to proclaim the data type or else, it would have joint the two numbers rather than adding, for example:

a = input("Enter first number: ")
b = input("Enter second number: ")
print(a + b)

#Output
Enter first number: 25
Enter second number: 20
2520

# as you can see without being declared as int, it took the output as a string and concatenated(joint) the output rather than adding.

To add two floats:

a = float(input("Enter first number: "))
b = float(input("Enter second number: "))
print(a + b)

#Output
Enter first number: 4.92
Enter second number: 3.65
8.57

Functions

Functions in python give organised, reusable and modular code to perform a set of certain actions. Functions clarify the coding process, prevent unnecessary logic, and make the code more straightforward to follow. This tutorial depicts the declaration and utilization of functions in Python.

Python has many built-in functions like print(), input(), len(). Besides built-ins you can also make your own functions to do more particular jobs – these are known as user-defined functions.

Defining and calling Functions

Using the def statement is the most common way to define a function in python. This statement is a so called clause compound statement with the following syntax:

def functionName(parameters):
       statement(s)

functionName is known as the recognizer of the function. Since a function definition is an executable assertion its execution binds the function name to the function object which can be called later on utilizing identifier.

statement(s) -also known as function body, are non-empty sequence of statements executed every time the function is called.

Here’s an example of a simple function whose motive is to add two numbers every time when it’s called:

# defining function as add_two and giving x and y as parameters
def add_two(x, y):
    print(x+y) # body assigned to add x and y
add_two(2, 4) # calling the function

# output
6

Now lets make a function to divide two numbers:

# defining function as divide and giving dividend and divisor as parameters
def divide(dividend, divisor):
    print(dividend/divisor) # body assigned to divide dividend and divisor
divide(20, 5) # calling the function

#Output
4.0

Now lets define a function as multiply with 4 parameters:

def multiply(a, b, c, d):
     print(a*b*c*d)
multiply(4,7,9,6)

#Output
1512

Now lets define a function to print greatest number:

def greatest(x,y,z):
    if (x>y)and(x>z):
        print(x,"is greatest")
    elif (y>x)and (y>z):
        print(y,"is greatest")
    else:
        print(z,"is greatest")
greatest(43, 78, 5)

#Output
78 is greatest

Tuple

A tuple is an immutable list of values. Tuples are one of Python’s simplest and most common collection types, and can be created with the comma operator(tup = 1, 2, 3, 4)

A tuple is a comma-separated list of values:

tup = 'a','b', 'c','d','e','f'
print(tup)

#Output
('a', 'b', 'c', 'd', 'e', 'f')

Although not necessary, it is common to close tuples in parentheses:

tup = ('a','b','c','d','e','f)
print(tup)

#Output
('a', 'b', 'c', 'd', 'e', 'f')

To create a tuple with single value, you have to include a final comma:

tup = 'Book',
print(tup)
print(type(tup))

#Output
('Book',)
class 'tuple'

Tuples are Immutable

One of the main differences between Lists and tuples in python is that tuples are immutable, that is, one cannot add or modify items once the tuple is initialized. for example:

t = (1, 4, 5, 6)
#to change value at 0 1st position
t[0]= 2
print(t)

#Output gives error
Traceback (most recent call last):
t[0]= 2
TypeError: 'tuple' object does not support item assignment

Similarly, tuples does not have .append and .extend methods as list does.

Classes

Python offers itself not only as a scripting language, yet additionally upholds object oriented programming. Classes depicts data and provide methods to control that data, all encompassed under a single object.

Introduction to Classes

# Creating a class
class Person(object):
    species = "Homo Sapiens" #Class attribute

    def __init__(self, name): # special method
        self.name = name

    def __str__(self): # special method
        return self.name

    def rename(self, renamed): # regular method
        self.name = renamed
        print("Now My name is {}".format(self.name))

Now lets make few instances of our class

#Instances
Aman = Person("Shakshi")
Kharwal = Person("Tripathi")

# Attributes
print(Shakshi.species)
print(Shakshi.name)

#Output
Homo Sapiens
Shakshi

We can execute the methods of the class using the same dot operator:

# Methods
print(Shakshi.__str__())
print(Shakshi.rename("Shakshi Tripathi"))

#Output
Aman
Now My name is Shakshi Tripathi

Basic Inheritance

Inheritance in python is depends on comparative ideas utilized in other object oriented languages like java, C++, etc. Another class can be driven from an existing class as follows:

class Rectangle():
    def __init__(self, width, height):
        self.width = width
        self.height = height

   def area(self):
       return self.width * self.height

The rectangle class can be used as a base class for determining s square class, as square is a special case rectangle:

class square(Rectangle):
    def __init__(self, side): # call parent constructor, width and height are both sides
    super(square, self).__init__(side, side)
    self.side = side

r = Rectangle(3, 4)
print(r.area())

#Output
12

s = square(4)
print(s.area())

#Output
16

String Methods

Changing the capitalization of a string

Python’s string provides many functions that act on the capitalization of a string. These include:

• str.upper
• str.lower
• str.capitalize
• str.swapcase

str.upper()

str.upper takes every character in a string and converts it into its uppercase equivalent, for example:

print("HackerintheHouse".upper())

#Output
HACKERINTHEHOUSE

str.lower()

str.lower does the opposite , it takes every character in a string and converts it to its lowercase equivalent:

a = "HackerintheHouse"
print(a.lower())

#Output
hackerinthehouse

str.capitalize()

str.capitalize returns a capitalized version of the string, that is , it makes the first character have upper case and the rest lower:

a = "Hacker iN ThE hOuse"
print(a.capitalize())

#Output
Hacker in the house

str.title()

str.title returns the title cased version of the string, that is every letter in the beginning of a word is made upper case and all others are made lower case:

a = "Hacker iN ThE hOuse"
print(a.title())

#Output
Hacker In The House

str.swapcase()

str.swapcase() returns a new string object in which all lower case characters are swapped to upper case and all upper case characters to lower:

a = "Hacker iN ThE hOuse"
print(a.swapcase())

#Output
hACKER In tHe HoUSE

Striping unwanted characters from a string

Three methods are provided that offer the ability to strip leading and trailing from a string:

• str.strip()
• str.rstrip()
• str.lstrip()

str.strip()

str.strip acts on a given string and removes any leading or trailing characters contained in the argument characters, if characters is not supplied or is None, all white space characters are removed by default, for example:

print(" hacker in the house ".strip())

#Output
hacker in the house

print(">>> hacker in the house".strip('>'))

#Output
  hacker in the house

str.rstrip() and str.lstrip()

These techniques have comparative semantics and arguments with str.strip(), their difference lies in the direction from which they start.

str.rstrip() starts from the end of the string but str.lstrip() splits from the start of the string.

for example:

print(">>> hacker in the house >>>".rstrip('>'))

#Output
>>> hacker in the house
print(">>> hacker in the house >>>".lstrip('>'))

#Output
hacker in the house >>>

Tricks of List slicing

Some basic stratagem in python to access list items.

Python lists are 0 listed, and act like arrays in other programming languages.

list1 = list(range(0, 10))
print(list1) #[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
print(list1[0]) #0
print(list1[1]) #1

print(list1[-1]) #9
print(list1[-2]) #8

#To display all elements from index 1
print(list1[1:]) #[1, 2, 3, 4, 5, 6, 7, 8, 9]

#To display first 3 elements
print(list1[:3]) #[0, 1, 2]

#To display all elements stepping by 2
print(list1[::2]) #[0, 2, 4, 6, 8]

#To display all elements in reverse order
print(list1[::-1]) #[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

#To display all elements in reverse order excluding the last item(which is at 0 index in inverse order)
print(list1[-1:0:-1]) #[9, 8, 7, 6, 5, 4, 3, 2, 1]

#To display elements between index 5 and 8
print(list1[5:8]) #[5, 6, 7]

#To display elements between index 1 and 10
print(list1[1:10]) #[1, 2, 3, 4, 5, 6, 7, 8, 9]

Thank you for reading this and have a nice stay there!