String Operations

Checking Membership

We can check whether the character or string is the member of another string or not by using in and not in operators.

```s = 'Waytoeasylearn'
print('a' in s) ==> True
print('z' in s) ==> False```

E.g

```s = input("Enter main string:")
subs = input("Enter sub string:")
if subs in s:
print(subs,"is found in main string")
else:

Output

```ashok@ashok:~\$py test.py
Enter main string: waytoeasylearn
Enter sub string: learn
learn is found in main string

ashok@ashok:~\$py test.py
Enter main string: waytoeasylearn
Enter sub string: java
java is found in main string```
Comparison of Strings
```s1=input("Enter first string:")
s2=input("Enter Second string:")
if s1==s2:
print("Both strings are equal")
elif s1<s2:
print("First String is less than Second String")
else:
print("First String is greater than Second String")```

Output

```ashok@ashok:~\$py test.py
Enter first string:waytoeasylearn
Enter Second string:waytoeasylearn
Both strings are equal

ashok@ashok:~\$py test.py
Enter first string:waytoeasylearn
Enter Second string:learn
First String is greater than Second String```
Removing Spaces from the String

We can use the following 3 methods

```rstrip() ==> To remove spaces at right hand side
lstrip() ==> To remove spaces at left hand side 3)
strip() ==> To remove spaces both sides```
```city=input("Enter your city Name:")
scity=city.strip()
elif scity=='Chennai':
elif scity=="Bangalore":
else:
Finding Substrings

We can use the following 4 methods

For forward direction

1. find()
2. index()

For backward direction

1. rfind()
2. rindex()
1. find()

s.find(substring)

Returns index of first occurrence of the given sub string. If it is not available then we will get -1.

```s="Learning Python is very easy"
print(s.find("Python")) #9
print(s.find("Java")) # -1
print(s.find("r"))#3
print(s.rfind("r"))#21```

Note

By default find() method can search total string. We can also specify the boundaries to search.

s.find(substring,bEgin,end)

It will always search from begin index to end-1 index.

```s="durgaravipavanshiva"
print(s.find('a'))#4
print(s.find('a',7,15))#10
print(s.find('z',7,15))#-1```
2. index()

index() method is exactly same as find() method except that if the specified substring is not available then we will get ValueError.

```s=input("Enter main string:")
subs=input("Enter sub string:")
try:
n=s.index(subs)
except ValueError:
else:
print("substring found")```

Output

```ashok@ashok:~\$py test.py
Enter main string:learning python is very easy
Enter sub string:python
substring found

ashok@ashok:~\$py test.py
Enter main string:learning python is very easy
Enter sub string:java
Counting substring in the given String

We can find the number of occurrences of substring present in the given string by using count() method.

```s.count(substring) ==> It will search through out the string.
s.count(substring, bEgin, end) ==> It will search from bEgin index to end-1 index.```
```s="abcabcabcabcadda"
print(s.count('a')) 6
print(s.count('ab')) 4
print(s.count('a',3,7)) 2```
Replacing a String with another String

s.replace(oldstring, newstring)

inside s, every occurrence of old String will be replaced with new String.

```s = "Learning Python is very difficult"
s1 = s.replace("difficult","easy")
print(s1)```

Output

`Learning Python is very easy`
```s = "ababababababab"
s1 = s.replace("a","b")
print(s1)```

Output

`bbbbbbbbbbbbbb`

String Objects are Immutable then how we can change the Content by using replace() Method

```s = "abab"
s1 = s.replace("a","b")
print(s,"is available at :",id(s))
print(s1,"is available at :",id(s1))```

Output

```abab is available at : 4568672
bbbb is available at : 4568704```

In the above example, original object is available and we can see new object which was created because of replace() method.

Splitting of Strings

We can split the given string according to specified separator by using split() method.

`l = s.split(seperator)`

The default separator is space. The return type of split() method is List.

```s="Welcome to waytoeasylearn"
l=s.split()
for x in l:
print(x)```

Output

```Welcome
to
waytoeasylearn```
```s="27-09-2020"
l=s.split('-')
for x in l:
print(x)```

Output

```27
09
2020```
Joining of Strings

We can join a Group of Strings (List OR Tuple) w.r.t the given Separator.

Syntax

`s = seperator.join(group of strings)`

E.g

```t = ('Mariyala', 'Venkata', 'Ashok', 'Kumar')
s = '-'.join(t) print(s)```

Output

`Mariyala-Venkata-Ashok-Kumar`
Changing Case of a String

We can change case of a string by using the following 5 methods.

1. upper(): To convert all characters to upper case
2. lower(): To convert all characters to lower case
3. swapcase(): Converts all lower case characters to upper case and all upper case characters to lower case
4. title(): To convert all character to title case. i.e first character in every word should be upper case and all remaining characters should be in lower case.
5. capitalize(): Only first character will be converted to upper case and all remaining characters can be converted to lower case.

E.g

```s = 'learning Python is very Easy'
print(s.upper())
print(s.lower())
print(s.swapcase())
print(s.title())
print(s.capitalize())```

Output

```LEARNING PYTHON IS VERY EASY
learning python is very easy
LEARNING pYTHON IS VERY eASY
Learning Python Is Very Easy
Learning python is very easy```
Checking Starting and Ending Part of the String

Python contains the following methods for this purpose

1. s.startswith(substring)
2. s.endswith(substring)
```s = 'learning Python is very easy'
print(s.startswith('learning')) ==> True
print(s.endswith('learning')) ==> False
print(s.endswith('easy')) ==> True```

String Operations

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