String Manipulation in Python

STRING MANIPULATION IN PYTHON
PROF POOJAB S

 Getting Length of a string
 Traversal through a string with a loop
 String slices
 Strings are immutable
 Looping and Counting
 The in operator
String Manipulation in Python

 String is a sequence of characters.
 Enclosed within pair of single/double quotes.
 Character has an index Number.
 Eg: “Hello World”
 Access characters using Index.
 Eg: word1='Hello'
word2='Hi'
x=word1[1]
print(x)
y=word2[0]
print(y)
Character H e l l o W o r l D
Index 0 1 2 3 4 5 6 7 8 9 10

 End of the string can be accessed using Negative Index.
 Eg: “Hello World”
 Eg: word=“Hello”
x=word[-1]
print(x)
x=word[-5]
print(x)
Character H e l l o W o r l
Negative Index -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1
d

Getting Length of a String using len()
 Built-in function
 Obtain length of a string.
 Eg: word="Python"
l=len(word)
print(l)
Traversal through String with a loop
 Extracting every character and performing some action is called Traversal.
 It can be done using while or for loop

1. Using for loop
s="Python"
for i in s:
print(i, end=‘t’)
2. Using while loop
s="Python"
i=0
while i<len(s): #FORWARD TRAVERSAL
print(s[i],end='t')
i=i+1
s="Python"
i=-1
while i>= -len(s): #BACKWARD TRAVERSAL
print(s[i],end='t')
i=i-1

String Slices
 Portion of a string is a string slice.
 Extract a required number of characters using colon (:)
 Syntax:
st[i:j:k]
 i is the first index or beginning index or start index
 j is the last index or end index. If j index is not present, means slice should be till the end of the string.
 k is the stride, to indicate no. of steps incremented. Default value is 1.
 Eg:
st=“Hello World”
print(st[0:5:1])

1. print (st[0:5])
2. print (st[3:8])
3. print (st[7:])
4. print (st[::])
5. print (st[::2])
6. print (st[4:4])
7. print (st[3:8:2])
8. print (st[1:8:3])
9. print (st[-4:-1])
10. print (st[-1])
11. print (st[:-1])
12. print (st[:])
13. print (st[::-1])
14. print (st[::-2])

 Strings are immutable [cannot change]
 To modify string, create a new string.
 Eg:
1. s="hello world“ #TypeError: 'str' object does not support item assignment
s[3]='t‘
2. s="hello world"
s1=s[:3]+'t'+s[4:] #helto world
print(s1)
String are immutable

 Using loops we can count the frequency of character.
 Eg:
w='Book'
count=0
for letter in w:
if letter=='o':
count=count+1
print("The Occurences of Character 'o' is %d"%(count))
Looping and Counting

 Boolean operator takes 2 string operands.
 Returns True if 1st operand appears in 2nd Operand. Else False.
 Eg:
‘el’ in ‘hello’ #True
‘x’ in ‘hello’ #False
‘EL’ in ‘Hello’ #False
The in operator

 Comparison operators like: <,> and == applied to string objects.
 Result in True or False
 Comparisons happens using ACSII codes
 Eg:
1. s='hello'
if s=='hello':
print('Same') #Same
2. s='hello'
if s<='Hello':
print('Lesser')
else:
print('Greater') #Greater
String Comparison

 A-Z 65-90
 a-z 97-122
 0-9 48-57
 Space 32
 Enter 13

String Manipulation in Python

More Related Content

What's hot

Similar to String Manipulation in Python

More from Pooja B S

Recently uploaded

String Manipulation in Python