String
str Data Type
The predefined data type str (string) is a collection data type.
A str is an ordered collection of elements.
The elements of the str have a position index starting with the value 0.
A variable of type str is a string of characters delimited by single, double or triple quotes.
A variable of type str is immutable: access to the characters constituting the str is read-only.
A str is limited and iterable: we can iterate over these elements in a for loop.
Access
We access the elements of a str using the [ ] and [:] operators.
Operations
The concatenation operator is the symbol +
The repetition operator is the symbol *
The membership operator is in
The non-membership operator is not in
The comparison operator is ==
Expression
'Hello ' + 'World!'
'toc' * 2
't' in 'Python'
Result
'Hello World!'
'toctoc'
True
Description
Concatenation
Repetition
Membership
Example
greet = 'Hello'
print (greet)
print (greet[0])
print (greet[2:5])
print (greet[2:])
print (greet * 2)
print (greet + ' World!')
Multiline String
Triple quotes are used to form a multi-line string.
Example
# multiline string
message = """
We can also create a multiline string in Python.
For this, we use three double quotes
or three single quotes
"""
print(message)
Iteration through a str
A str is limited and iterable: we can iterate over its elements in a for loop.
We use the membership operator in to iterate over the elements of a str.
Example
greet = 'Hello'
# iterate through the string
for letter in greet:
print(letter)
str Length
The length of a str is the number of characters it contains.
The len() function returns the length of a str.
Example
greet = 'Hello'
print('String length: ', len(greet))
f-Strings Format
The f-Strings format makes it easy to display values and variables.
Example
name = 'apple'
family = 'fruit'
print(f'{name} is a {family}')
Methods
List of some methods defined in the str class.
Method
Description
upper()
Converts string to uppercase.
lower()
Converts string to lowercase.
partition()
Partitions the string, returns a tuple.
replace()
Replace a substring.
find()
Returns the index of the first occurrence of a substring.
rstrip()
Removes trailing space characters.
split()
Splits string from left, returns a list.
startswith()
Checks if the string starts with a specified string.
Example
a = 'Learn Coding'
print(a.upper())
print(a.lower())
b = a.replace('Coding', 'Python')
print(b)
k = b.find('Python')
print(k)
c = 'docs.python.org'
tpl = c.partition('.')
print(tpl)
lst = c.split('.')
print(lst)