Python - Strings

Python Strings

Strings are one of the most common data types in Python. It is used for storing text. It can be created by enclosing characters either in single quotation marks or double quotation marks. It can be assigned to a variable using = sign.

MyString = "Hello World!"
MyString = 'Hello World!'

Python Multi-line Strings

Multi-line string can be created by enclosing the block either in three single quotation marks or three double quotation marks.

MyString = """Python 
programming"""

MyString = '''Python 
programming'''

Access character of a String

A character (also called element) of a string can be accessed with it's index number. In Python, index number starts with 0 in forward direction and -1 in backward direction. The below figure and example describe the indexing concept of a string.

String Indexing:

MyString = 'Python'

#forward indexing
print(MyString[0]) 

#backward indexing 
print(MyString[-1])  

P 
 
n   

Access range of characters of a String

Range of characters of a string can be selected using statement like [start_index : end_index] where end_index is excluded. If start_index and end_index are not mentioned then it takes first and last index numbers of the string respectively.

MyString = 'Learn Python'
print(MyString[0:5])
print(MyString[-12:-7])

print(MyString[6:])
print(MyString[:-7])

print(MyString[:])

Learn
Learn

Python
Learn

Learn Python   

String Length

The len() function can be used to find out total number of characters in the string.

MyString = 'Learn Python'
print(len(MyString))

12

Check a character(s) in the String

If control statement is used to check whether the string contains specified character(s) or not.

MyString = 'I am learning Python programming.'
if 'programming' in MyString:
  print('Yes, It is present in the string.')
else:
  print('No, It is not present in the string.')

Yes, It is present in the string.

String Concatenation

Two strings can be joined using + operator.

text_1 = 'Learn'
text_2 = 'Python'
MyString = text_1 + text_2
print(MyString)

MyString = text_1 + " " + text_2
print(MyString)

LearnPython

Learn Python

String format() Method

Strings can not be added with numbers by using + operator. For combining string with a number, format method is used. A user can pass parameter(s) in format() method, which is further placed into its respective placeholder {}. This method can take unlimited number of parameters. Along with this, an index number (starts with 0) can also be used with placeholders. Please see example below:

Example:

in_time = 9
out_time = 18
MyString = "I will reach office at {} hrs and leave office at {} hrs."
print(MyString.format(in_time, out_time))

in_time = 9
out_time = 18
MyString = "I will reach office at {1} hrs and leave office at {0} hrs."
print(MyString.format(out_time, in_time))

I will reach office at 9 hrs and leave office at 18 hrs.

I will reach office at 9 hrs and leave office at 18 hrs.

String Methods

Python has number of . Here, few very common string functions are discussed.

• lower(): Returns string in lowercase
• upper(): Returns string in uppercase
• strip(): Removes whitespaces from start and end of the string
• replace(): replace specified character(s) with another specified character(s)
• split(): Split the string by specified separator and returns substrings in a list.
• count(): Returns number of occurrence of specified character(s) in the string

Example: lower(), upper() and strip() String Methods

MyString = "Learn Python"
print(MyString.lower())
print(MyString.upper())

MyString = "  Learn Python  "
print(MyString.strip())

learn python

LEARN PYTHON

Learn Python

Example: replace(), split() and count() String Methods

MyString = "Learn Python"
print(MyString.replace("Python", "C++"))

MyString = "Learning Python is fun"
print(MyString.split(" "))

MyString = "This is Python programming."
print(MyString.count('is'))

Learn C++

['Learning', 'Python', 'is', 'fun']

2