Strings and Characters

Strings and Characters

"""A Python program to access each element of a string

in forward and reverse orders using while loop"""

#indexing on string

s="Rama Rao"

#Accessing each character using while loop

n=len(s) #n is no of chars in string s

i=0 #i varies from 0 to n-1

while i>=-n:

    print(s[i],end=' ')

    i=i-1 #i-=1

print() #put curson into next line

#access in reverse order using negative index

i=1 #where i varies from 1 to n

n=len(s) # no of characters in String s

while i<=n:

    print(s[-i],end=' ')

    i=i+1 #i+=1

   

"""output:

R o a R   a m a R

o a R   a m a R

>>> """

Indexing in Strings

Index represents the position number. Index is written using square braces []. By specifying the position number through an index, we can access the particular elements or characters of a string.

Negative number:

When we use index as a negative number, it can access the elements in the reverse order that is s[-1] refers to the last element.

"""A Python program to access each element of a string

in forward and reverse orders using for loop"""

#indexing on string

s="Rama Rao"

#access each letter using for loop

for i in s:

    print(i,end='')

print()#new line

#access in reverse order

for i in s[::-1]:

    print(i,end='')

"""output:

Rama Rao

oaR amaR

>>>

>>> """

Slicing the String

A slice represents a part or piece of a string.

String[start:stop:stepsize]

S=’Rama Rao’

S[0:7:1]

>>> s[0:7:1]

'Rama Ra'

>>> s[0:7:2]

'Rm a'

>>> s[::]#access string from 0^th to last character

'Rama Rao'

>>> s[::2] #Access entire string in steps of 2

'Rm a'

>>> s[2::]#access string from s[2] to ending

'ma Rao'

>>> s[2:4:1] #access from s[2] to s[3] in steps of 1

'ma'

>>> 

Suppose if you write the following statements:

>>> s[:3:] #accessing string from s[0] to s[2] in steps of 1

'Ram'

>>> 

It is possible to use reverse slicing to retrieve the elements from the string in reverse order.

>>> s[-4:-1]

' Ra'

>>> 

>>> s[-8::]

'Rama Rao'

>>> 

Concatenation of Strings

>>> a='mahesh'

>>> b='babu'

>>> c=a+b

>>> print(c)

maheshbabu

>>> 

We can use ‘+’ on strings to attach a string at the end of another string. If we use ‘+’ operator on numbers it is called addition operators, When we used on strings, it is called ‘concatenation’ operator since it joins the strings.

Removing Spaces from a string:

s=" Rama "

>>> print(s.strip())

Rama

>>> print(s)

 Rama

>>> print(s.lstrip())

Rama

>>> print(s.rstrip())

 Rama

>>> 

Related Video: https://www.youtube.com/watch?v=KfN8GsNZo1E&feature=youtu.be


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