Python - Strings

In Python, a string is an immutable sequence of Unicode characters. Each character has a unique numeric value as per the UNICODE standard. But, the sequence as a whole, doesn’t have any numeric value even if all the characters are digits. To differentiate the string from numbers and other identifiers, the sequence of characters is included within single, double or triple quotes in its literal representation. Hence, 1234 is a number (integer) but ‘1234’ is a string.

Creating Python Strings

As long as the same sequence of characters is enclosed, single or double or triple quotes don’t matter. Hence, following string representations are equivalent.

Example

>>> 'Welcome To TheMakPro'
'Welcome To TheMakPro'
>>> "Welcome To TheMakPro"
'Welcome To TheMakPro'
>>> '''Welcome To TheMakPro'''
'Welcome To TheMakPro'
>>> """Welcome To TheMakPro"""
'Welcome To TheMakPro'

Looking at the above statements, it is clear that, internally Python stores strings as included in single quotes.

In older versions strings are stored internally as 8-bit ASCII, hence it is required to attach ‘u’ to make it Unicode. Since Python 3, all strings are represented in Unicode. Therefore, It is no longer necessary now to add ‘u’ after the string.

Accessing Values in Strings

Python does not support a character type; these are treated as strings of length one, thus also considered a substring.

To access substrings, use the square brackets for slicing along with the index or indices to obtain your substring. For example −

var1 = 'Hello World!'
var2 = "Python Programming"

print ("var1[0]: ", var1[0])
print ("var2[1:5]: ", var2[1:5])

When the above code is executed, it produces the following result −

var1[0]:  H
var2[1:5]:  ytho

Updating Strings

You can “update” an existing string by (re)assigning a variable to another string. The new value can be related to its previous value or to a completely different string altogether. For example −

var1 = 'Hello World!'
print ("Updated String :- ", var1[:6] + 'Python')

When the above code is executed, it produces the following result −

Updated String :-  Hello Python

Escape Characters

Following table is a list of escape or non-printable characters that can be represented with backslash notation.

An escape character gets interpreted; in a single quoted as well as double quoted strings.

String Special Operators

Assume string variable a holds ‘Hello’ and variable b holds ‘Python’, then −

String Formatting Operator

One of Python’s coolest features is the string format operator %. This operator is unique to strings and makes up for the pack of having functions from C’s printf() family. Following is a simple example −

print ("My name is %s and weight is %d kg!" % ('Zara', 21)) 

When the above code is executed, it produces the following result −

My name is Zara and weight is 21 kg!

Here is the list of complete set of symbols which can be used along with % −

Other supported symbols and functionality are listed in the following table −

Double Quotes in Python Strings

You want to embed some text in double quotes as a part of string, the string itself should be put in single quotes. To embed a single quoted text, string should be written in double quotes.

Example

var = 'Welcome to "Python Tutorial" from TheMakPro'
print ("var:", var)

var = "Welcome to 'Python Tutorial' from TheMakPro"
print ("var:", var)

It will produce the following output −

var: Welcome to "Python Tutorial" from TheMakPro
var: Welcome to 'Python Tutorial' from TheMakPro

Triple Quotes

To form a string with triple quotes, you may use triple single quotes, or triple double quotes − both versions are similar.

Example

var = '''Welcome to TheMakPro'''
print ("var:", var)

var = """Welcome to TheMakPro"""
print ("var:", var)

It will produce the following output −

var: Welcome to TheMakPro
var: Welcome to TheMakPro

Python Multiline Strings

Triple quoted string is useful to form a multi-line string.

Example

var = '''
Welcome To
Python Tutorial
from TheMakPro
'''
print ("var:", var)

It will produce the following output −

var:
Welcome To
Python Tutorial
from TheMakPro

Arithmetic Operators with Strings

A string is a non-numeric data type. Obviously, we cannot use arithmetic operators with string operands. Python raises TypeError in such a case.

print ("Hello"-"World")

On executing the above program it will generate the following error −

>>> "Hello"-"World"
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for -: 'str' and 'str'

Getting Type of Python Strings

A string in Python is an object of str class. It can be verified with type() function.

Example

var = "Welcome To TheMakPro"
print (type(var))

It will produce the following output −

<class 'str'>

Built-in String Methods

Python includes the following built-in methods to manipulate strings −

Built-in Functions with Strings

Following are the built-in functions we can use with strings −