find substring():

• The find substring is used to find the substring from the string.
• Substring is the piece of characters from the string.
• If the string consists of the given string then it returns the index number of the substring. 
• The string must be enclosed with single or double-quotes.
• It returns -1 if the substring does not found instead of an error.
• find() has 3 parameters,they are:

#write a python code to demonstrate the find substring function.

• In python, replace all is similar to replace() function. 
• Here we are going to replace all the characters with new characters.
• It also consists of 3 parameters like new value, old value, count.
• The old value is the string that we have already given in string.
• The new value is the that is to be replaced with.
• The count is the number of times that string to be replaced in the string.

#write a python code to demonstrate the replace function.

•  The format() function is used to format a specific value and insert that value in string placeholders.
•  The placeholders are cost{20}, number index{1},empty{}
• The place holder is defined by" curly braces"{}.
• The format function consists of parameters called value.
• It returns the formatted string.

• Inside the placeholders, we can add different formatting types
• :+    indicates positive values.
• : -    indicates negative values.
• :      indicates the space before positive and also negative numbers.
• :_    indicates as a thousand separator.
• :,     uses as comma thousand separator.
• :=    left most position.
• :<    result in left alignment.
• :>    result in right alignment.
• :^     result in the center.
• :%    percentage format.
• :b     Binary format.
• :c     Unicode format.
• :d     Decimal format.
• :e      format with lower case.
• :E     format with upper case.
• :f      format with fixpoint number.
• :o    format is octal.
• :x      format is Hexa.
• :X     format is Hexa in uppercase.
• :n      number format.

#write a python code to demonstrate format function.

• The reverse string in python is not an in-built function.
• By creating the slice operation we can perform the reverse function.
• In this slice operation, we create the slice that starts with the end of the string and moves backward.
• String reverse in python example program

                     gfedcba

 right to left indexing:              [-7]    [-6]    [-5]    [-4]      [-3]     [-2]      [-1]

                                                    a          b      c        d          e          f         g 

left to right indexing:             [0]         [1]     [2]     [3]     [4]       [5]        [6]

• In the above example, we are having the string  "abcdefg " which we want to reverse. so create a slice that starts with the end of the string and moves backward.
• here it starts with the end index that is indicated with -1 and moves backward as 5,4,3,2,1,0.
• -1 index  is g
• 5 index is f
• 4 index is e
• 3 index is d
• 2 index is c
• 1 index is b
• 0 index is a
• so the final output is gfedcba.

#write a python code to demonstrate string reverse.

1. txt="today climate is very cool"[::-1]
2. txt1="hello world"[::-1]
3. print(txt)
4. print(txt1)

Output:    looc yrev si etamilc yadot

                  dlrow olleh

•  In python, to lower is used to convert the uppercase letters to lower case.
• It uses the function called lower().
• It doesn't have any parameters.
• The string must be enclosed with single or double-quotes.
• If the string does not contain any upper case letters then it returns the same string.

Example: s="HELLO"

             str.lower(s)=hello

#write a python code to demonstrate the lower() function.

•  In python, we have different functions which remove the spaces between the strings.
• There are three functions that remove the whitespace between the strings, they are:
• strip(), rstrip(), lstrip()  are the three functions having the same meaning but some differences.

syntax: str.strip()

lstrip(): It removes the whitespace at beginning of the string.

syntax: str.rstrip()

rstrip(): It removes the whitespace at end of the string.

syntax: str.rstrip()

Example: write a python to demonstrate the remove space function.

1. txt="    hello"
2. print(txt)
3. print(txt.strip())
4. print(txt.rstrip())
5. print(txt.lstrip())