Python Tutorial for Beginners Part 2

Strings:-

Strings include letters, special characters, spaces, digits, etc.
It is enclosed in single quotes ( ‘ ‘ ) or double quotes ( ” ” ).
str = "Cyber Connaught"

We can concatenate strings

str = "Cyber Connaught"
welcome_str = "Welcome to our website"
concate_str = welcome_str + str
print(concate_str)
> Welcome to our websiteCyber Connaught

Covered Topics

• Strings
• Indexing
• Slicing
• Input
• Comparison Operators
• Logical Operators

To get it in a proper way

1. Concate_str = welcome_str + " " + str
2. Just give some space in welcome_str at end

welcome_str = "Welcome to our website"
print(concate_str = welcome_str + " " + str) 
> Welcome to our website Cyber Connaught

welcome_str = "Welcome to our website "
concate_str = welcome_str + str
print(concate_str)
> Welcome to our website Cyber Connaught

One of the operations on a string is defined in python docs.

str = "Conrado"
str_3 = "My name is " + str * 3 + "!"
> My name is ConradoConradoConrado!

We can calculate the length of the string by len().

name = "Conrado"
len(str)
> 7

sur_name = "Torres"
full_name = name + " " + sur_name
len(full_name)
> 14

Indexing:-

We can get a specific character as a variable or output in a string by indexing the string. An index is a position in a string. In Python indexing start from 0.

The first character is at an index of 0
The second character is at index 1
and goes on…..

name = "Conrado Torres"

	C	o	n	r	a	d	o		T	o	r	r	e	s
	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14
-15	-14	-13	-12	-11	-10	-9	-8	-7	-6	-5	-4	-3	-2	-1

print(name[2])
>n

print(name[6])
>o

print(name[12])
>e

How do you print the last character of a string?
str = "pneumonoultramicroscopicsilicovolcanokoniosis"
We can use two simple methods to get the last character.

char = str[len(str) - 1]
print(char)
> s

print(str[-1])
> s

python uses negative indexing to count from the end.

Slicing:-

We can get a subset of characters by slicing.
steps:-

• get the starting index of the slice
• separate with a column
• get the ending index of the slice

str [ i : j ] gives you characters at index
i , i + 1 , i + 2 , … , j – 1

Once go through the following tables and the following problems.

name = "Cyber Connaught"

	C	y	b	e	r		C	o	n	n	a	u	g	h	t
	0	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15
-16	-15	-14	-13	-12	-11	-10	-9	-8	-7	-6	-5	-4	-3	-2	-1

Examples –

name[6:13] > ‘Connaug’	name[0:5] > ‘Cyber’	name[6:15] > ‘Connaught’
name[6:-2] > ‘Connaug’	name[:5] > ‘Cyber’	name[6:] > ‘Connaught’

1)	name [4:7] ‘r C’	name[-11:-8] ‘r C’	name[4:-8] ‘r C’	name[-11:7] ‘r C’
2)	name[:] ‘Cyber Connaught’	name[::] ‘Cyber Connaught’	name[0:] ‘Cyber Connaught’	name[:15] ‘Cyber Connaught’

Input:-

variable = input("Write some thing you want from user")

Example –

name = input("Enter your name..")
     
#input statement
> Enter your name.. Cyber Connaught  #you have to enter name

# Now, name = "Cyber Connaught"
print("Your name is " + name)

> Your name is Cyber Connaught

Input gives you a string so you must cast if working with numbers.

Examples –

num = input("Ënter the number ")
> Enter the number 3
print(3*num)
> 333

num = int(input("Ënter the number "))
> Enter the number 3
print(3*num)
> 9

Write a program that will ask your name and your age and then print it out like
“My name is ‘name’ and I am ‘age’ years old”

name = input("Enter your name ")
age = input("Enter your age ")
print("My name is " + name + " and I am " + age + " years old.")

Comparison Operators:-

Let’s take i and j variable names. The output of the comparison evaluates to a Boolean value.

1.	i > j	i greater than j	5 > 3		True
2.	i >= j	i greater than or equal to j	5 >= 3	5 >= 5	True
3.	i < j	i less than j	3 < 5		True
4.	i <= j	i less than or equal to j	3 <= 5	5 <= 5	True
5.	i == j	i equal to j	3 == 3	3 == 3.0	True
6.	i != j	i not equal to j	3 != 5		True

Logical Operators:-

There are three operators not, and, or

• not negates the Boolean value
• and returns True only if both statements are True.
• or returns False only if both statements are False.

Just here for better understanding take :- ( True = 1 ) , ( False = 0 )

Sr.no	a	b	not a	not b	a and b	a or b
1	0	0	1	1	0	0
2	0	1	1	0	0	1
3	1	0	0	1	0	1
4	1	1	0	0	1	1

Examples –

a , b ,c = 6 , 8 , 4
a > b
## False
not (a > b)
## True
(a > b) and (b > a)
## False
(a > b) or (b > a)
## True
(a < c) or ((b > c) and not (a < c))
## True

work_time = 15
sleep_time = 8
print(sleep_time < work_time)
## True

work_time = 15
sleep_time = 8
print(sleep_time > work_time)
## False

sports = True
games = False
both = sports and games
print(both)
## False

Here sports can get its value by another function or equation by a sequence of logical steps.

sports = 3>2 ( Equation )
games = False
both = sports and games
print(both)
## False