Introduction of String

What is String in Python?

A string is a sequence of characters.A character is simply a symbol. For example, the English language has 26 characters 

In Python, a string is a sequence of Unicode characters. Unicode was introduced to include every character in all languages and bring uniformity in encoding. You can learn about Unicode from Python Unicode.

Strings are immutable. This means that elements of a string cannot be changed once they have been assigned.

How to create a string in Python?

Strings can be created by enclosing characters inside a single quote or double-quotes. Even triple quotes can be used in Python but generally used to represent multiline strings and docstrings.

# defining strings in Python
mystring = 'Hello'
print(mystring)

mystring = "Hello"
print(mystring)

mystring = '''Hello'''
print(mystring)

# triple quotes string can extend multiple lines
mystring = """Hello, welcome to
           the world of Python"""
print(mystring)

  

  When you run the program, the output will be:

 Hello

Hello
Hello
Hello, welcome to
           the world of Python

How to access characters in a string?

String Indexing

We can access individual characters using indexing and a range of characters using slicing. Index starts from 0. Trying to access a character out of index range will raise an IndexError. The index must be an integer. We can't use floats or other types, this will result into TypeError.

The index of -1 refers to the last item, -2 to the second last item and so on. We can access a range of items in a string by using the slicing operator :(colon).

#Accessing string characters in Python
str = 'programiz'
print('str = ', str)

#first character
print('str[0] = ', str[0])

#last character
print('str[-1] = ', str[-1])

#slicing 2nd to 5th character
print('str[1:5] = ', str[1:5])

#slicing 6th to 2nd last character
print('str[5:-2] = ', str[5:-2])

When you run the program, the output will be:

str =  programiz
str[0] =  p
str[-1] =  z
str[1:5] =  rogr
str[5:-2] =  am

Python String Operations

There are many operations that can be performed with string which makes it one of the most used data types in Python.

Concatenation of Two or More Strings

Joining of two or more strings into a single one is called concatenation.

The + operator does this in Python. Simply writing two string literals together also concatenates them.

The * operator can be used to repeat the string for a given number of times.

# Python String Operations
str1 = 'Hello'
str2 ='World!'

# using +
print('str1 + str2 = ', str1 + str2)

# using *
print('str1 * 3 =', str1 * 3)

When we run the above program, we get the following output:

str1 + str2 =  HelloWorld!
str1 * 3 = HelloHelloHello

If we want to concatenate strings in different lines, we can use parentheses.

>>> # using parentheses
>>> s = ('Hello '
...      'World')
>>> s
'Hello World'

String Membership Test

We can test if a substring exists within a string or not, using the keyword in.

>>> 'a' in 'program'
True
>>> 'at' not in 'battle'
False

Iterating or Traversing Through a string

We can iterate through a string using a for loop. Here is an example to count the number of 'l's in a string.

# Iterating through a string
count = 0
for letter in 'Hello World':
    if(letter == 'l'):
        count += 1
print(count,'letters found')

When we run the above program, we get the following output:

3 letters found

Raw String to ignore escape sequence

Sometimes we may wish to ignore the escape sequences inside a string. To do this we can place r or R in front of the string. This will imply that it is a raw string and any escape sequence inside it will be ignored.

>>> print("This is \x61 \ngood example")
This is a
good example
>>> print(r"This is \x61 \ngood example")
This is \x61 \ngood example




Common Python String Methods

There are numerous methods available with the string object. The format() method that we mentioned above is one of them. Some of the commonly used methods are lower(), upper(), join(), split(), find(), replace() etc. Here is a complete list of all the built-in methods to work with strings in Python.

>>> "PrOgRaMiZ".lower()
'programiz'
>>> "PrOgRaMiZ".upper()
'PROGRAMIZ'

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Milan Tomic

Hi. I’m Designer of Blog Magic. I’m CEO/Founder of ThemeXpose. I’m Creative Art Director, Web Designer, UI/UX Designer, Interaction Designer, Industrial Designer, Web Developer, Business Enthusiast, StartUp Enthusiast, Speaker, Writer and Photographer. Inspired to make things looks better.

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