res = a+b
print(f'{a}+{b}={res}')

res = a-b
print(f'{a}-{b}={res}')

res = a*c
print(f'{a}+]*{c}={res}')

res = c/a
print(f'{c}/{a}={res}')

res = c//a
print(f'{c}//{a}={res}')

res = b**a
print(f'{b} to the power of {a}={res}')

Text

In python programming, text which is called a string, is a sequence of characters enclosed within a single quote(‘.......’) or double quote(“..................”). The string value is represented as str data type.

# both variable contains same value: hello world
msg1 = "hello world"
msg2 = 'hello world'

print(msg1)
print(msg2)

To quote a quote, we need to “escape” it, by preceding it with  \

a = 'He doesn\'t want to out'
print(a)

b = '"Hello!" How are you?'
print(b)

Operations on string

string can be concatenated using + operator

a = 'hello'
b = 'world'

# string can be concatenated using + operator
c = a+b
print(c)

# string values next to each other is also automatically concatenated
res = 'Thank' 'you'
print(res)

Python also supports the use of * operator, by string repetitions, for 'val'*num, val is repeated num number of times.

res = 'hello'*2
print(res)

Indexing in string

In Python programming, string is a collection of characters, enclosed within quotes. Individual characters in string can be accessed by using Index, from left to right, the characters in strings are indexed from 0 to length of string-1. Note: There is no separate character data type in string, each character that we access using index is simply string of size 1. syntax to index the string to get substring is as:

variable_name[ index ]

a = "Python"
print(a[0])
print(a[1])
print(a[2])

Another utility function commonly used in python is len() its  syntax is:

Signature: len(obj, /)

Docstring: Return the number of items in a container.

function len() is commonly used to calculate length or size of a given container.

# we can get number of character in the given string as:
a = "Python"
length = len(a)
print(f'Length of given string is: {length}')

# since strings are indexed from 0 to size of string-1
# we can get last character in string as:
a = "Programming"
print(a[len(a)-1])

Unlike other programming languages, python also supports negative indexing from right to left. The concept makes it very convenient for programmers to access the last character of the string.

b = "Test"
print(b[-1])
print(b[-2])

Slicing python string

In python programming, indexing is used to get single character while slicing operation can be used to get substring from the given string.The basic form of slicing operation is as:

Variable_name[start_index:end_index]

By default start_index=0 while end_index=-1

# slicing operation, for slicing operation the given string is treated as:
+----+----+-----+----+----+----+
P    |  y |  t  |  h |  o |  n |
+----+----+-----+----+----+----+
0    1    2     3    4    5    6
-6  -5   -4    -3   -2   -1

a = "Python"
# inorder to get substring "yth", we need to perform slicing as follows:
a[1:4]

b = "Hello"
#to get substring "Hell", we can perform operation as follows:
print(b[0:3])
print(b[:3]) # as default startindex is 0
# to get substring "llo"
print(b[2:5])
print(b[2:]) # by default last index is -1 or len(b)

InBuilt String functions

In python programming, when we create a string variable as:

a = "Python"

Here a is an object or instance of class<str>, so variable a which is an object of class str can access all the methods defined for str class. [Note: object and class is a concept related to object oriented programming. So python programming language is object oriented programming, all variables we create in python are actually instances of some classes.]

Python provides a built-in method called dir(), to list all available methods for that particular class,object or values. let us see all the method available for string class:

name = "Hello world"
print(dir(name)) 

The output below list all the method available for string class:

['__add__', '__class__', '__contains__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__getitem__', '__getnewargs__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__iter__', '__le__', '__len__', '__lt__', '__mod__', '__mul__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__rmod__', '__rmul__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'capitalize', 'casefold', 'center', 'count', 'encode', 'endswith', 'expandtabs', 'find', 'format', 'format_map', 'index', 'isalnum', 'isalpha', 'isascii', 'isdecimal', 'isdigit', 'isidentifier', 'islower', 'isnumeric', 'isprintable', 'isspace', 'istitle', 'isupper', 'join', 'ljust', 'lower', 'lstrip', 'maketrans', 'partition', 'removeprefix', 'removesuffix', 'replace', 'rfind', 'rindex', 'rjust', 'rpartition', 'rsplit', 'rstrip', 'split', 'splitlines', 'startswith', 'strip', 'swapcase', 'title', 'translate', 'upper', 'zfill']

Following are most commonly used string methods:

• capitalize(): Returns a copy of the string with its first character capitalized.

text = "hello world"
result = text.capitalize()
print(result)  # Output: Hello world

• casefold(): Returns a casefolded version of the string. Casefold is similar to lowercase, but more aggressive for Unicode characters.

text = "Hello World"
result = text.casefold()
print(result)  # Output: hello world

• center(width[, fillchar]): Returns a centered string of specified width with optional fill character.

text = "hello"
result = text.center(10, '*')
print(result)  # Output: **hello***

• count(sub[, start[, end]]): Returns the number of occurrences of a substring in the given range.

text = "hello world, hello universe"
count = text.count("hello")
print(count)  # Output: 2

• encode([encoding[, errors]]): Returns an encoded version of the string.

text = "hello"
encoded = text.encode('utf-8')
print(encoded)  # Output: b'hello'

• endswith(suffix[, start[, end]]): Returns True if the string ends with the specified suffix.

text = "hello world"
result = text.endswith("world")
print(result)  # Output: True

• find(sub[, start[, end]]): Returns the lowest index of the substring, or -1 if not found.

text = "hello world"
index = text.find("world")
print(index)  # Output: 6

• **format(*args, kwargs): Formats the string using placeholders.

name = "John"
age = 25
result = "My name is {} and I am {} years old.".format(name, age)
print(result)  # Output: My name is John and I am 25 years old.

• index(sub[, start[, end]]): Returns the lowest index of the substring, or raises ValueError if not found.

text = "hello world"
index = text.index("world")
print(index)  # Output: 6

• isalnum(): Returns True if all characters in the string are alphanumeric.

text = "hello123"
result = text.isalnum()
print(result)  # Output: True