By: Archana Shukla and Rajesh Shukla
Strings
String is a sequence of characters surrounded by either single quotation marks, or double quotation marks.
‘hello’ is the same as “hello”.
Assign String to a Variable
Assigning a string to a variable is done with the variable name followed by an equal sign and the string:
Example
>>>a = “Hello”
>>>print(a)
Multiline Strings
You can assign a multiline string to a variable by using three quotes: we can use three double quotes or three single quotes
Example
>>>a = “””A string can hold
any type of known characters
of any scripted language .”””
>>>print(a)
Example
>>>a = ‘’’A string can hold
any type of known characters
of any scripted language .’’’
>>>print(a)
String operations
Concatenation
Joins two strings. ‘+’ operator is used for joining two strings.
Example
>>> str1=’hello’
>>> str2=’world’
>>> print(str1+str2)
helloworld
Repetition
Creates multiple copies of same string. ‘*’ operator is used.
Example
>>> str1=’hello’
>>> print(str1*3)
hellohellohello
Membership
in and not in. Returns true if the given character exists in the string.
Example
>>> str1=’hello’
>>> str2=’world’
>>> print(‘h’ in str1)
True
>>> print(‘W’ in str2)
False
String Slicing
A slice of string is nothing but a substring. A chunk of characters can be extracted by using the slice syntax. Specify the start index and the end index, separated by a colon, to return a part of the string.
Example
>>>b = “Hello, World!”
>>>print(b[2:5]) #this code segment will display ‘llo’
Negative Indexing
Negative indexes are used start the slice from the end of the string:
Example
>>>b = “Hello, World!”
>>>print(b[-5:-2]) # this code segment will display ‘orl’
Built-in String methods
| Method | Description | Example |
| isalpha() | Returns true if the string contains only alphabets | >>>str=’Good’ >>>print(str.isalpha()) True |
| isdigit() | Returns true if the string contains only digits | >>>str=’123456’ >>>print(str.isdigit()) True |
| lower() | Converts all the uppercase letters in the string to lower case | >>>str=’GOOD’ >>>print(str.lower()) good |
| upper() | Converts all the lowercase letters in the string to uppercase | >>>str=’good’ >>>print(str.lower()) GOOD |
| islower() | Returns true if all the letters in the string are lowercase | >>>str=’good’ >>>print(str.islower()) True |
| isupper() | Returns true if all the letters in the string are uppercase | >>>str=’GOOD’ >>>print(str.isupper()) True |
| lstrip() / lstrip(chars) | Returns the string after removing spaces from the left side of the string | >>>str=” hello world” >>>print(str.lstrip()) “hello world” >>>str=”hello world” >>>print(str.lstrip(he)) “llo world” |
| rstrip() / rstrip(chars) | Returns the string after removing spaces from the right side of the string | >>>str=”hello world ” >>>print(str.lstrip()) “hello world” >>>str=”computers” >>>print(str.lstrip(rs)) “compute” |
| isspace() | Returns true if the string contains only spaces otherwise false | >>>str=” “ >>>print(str.isspace()) True >>>str=” computer “ >>>print(str.isspace()) False |
| istitle() | If the first letter of each word in the string are uppercase, this functions returns true otherwise false. | >>>str=”Revision Tour In Pyhton“ >>>print(str.istitle()) True |
| join(sequence) | This method takes all items in an iterable and joins them into one string using a specified character | >>>str=”12345” >>>x=“-“.join(str()) >>>print(x) 1-2-3-4-5 |
| swapcase() | Make the lower case letters upper case and the upper case letters lower case | >>>str=”Revision Tour In Pyhton“ >>>print(str.swapcase()) rEVISION tOUR iN pYHTON |
| partition(separator) | This method searches for a specified string, and splits the string into a tuple containing three elements. | >>>str = “I could eat bananas all day” >>>x=str.partition(“bananas”) >>>print(x) (‘I could eat’, ‘bananas’, ‘all day’) |
| ord() | Returns the ASCII value of the specified character | >>>ch=’b’ >>>ord(ch) 98 |
| chr() | Returns the character represented by given ASCII value. | >>>n=66 >>>chr(n) B |
