String Variable In Python

1. Define a string in Python

Like all other programming languages, strings in python is a sequence of Unicode characters taken as a Python variable in the form of expressions surrounded by single quotes or double quotes. For example “Python Programming” is a Python string identical to ‘Python Programming’.

Python Strings can be displayed on screen using the print() function:

print(name_of_the_string_variable)

Like many other popular programming languages, strings in Python are byte arrays representing Unicode characters. However, Python does not have a character (char) data type like char type in C, a single character is simply a string of length 1. Square brackets can be used to access string elements.

2. Length of a Python string

The length of a character string is by definition the number of characters that make up the string. To get the length of a string, we use the len() method.

Example: length of the string s = “Python”

s = "Python"
print("The length of the string s is:", len(s)) 
# output: The length of the string s is: 6

3. Accessing the elements of a Python string

To access an element of a character string s, we use the syntax:

s[character_index]

Example

Let’s have fun displaying the first and second character of the string: s = “Python Programming”
(remember that the first character is at position 0):

s = "Python Programming"
print("the first character of s is: ", s[0])
# displays: "the first character of s is 'P'
print("the second character of s is: ", s[1])
# displays:"the second character of s is 'y'

Example: displaying all characters of a string using the len() method

s="Python"
for i in range(0 , len(s)):
    print(s[i])
# attach:
"""
P
y
t
h
o
n
"""

Example: displaying total characters of a string via the iterator method

s="Python"
for x in s:
    print(x)
# output:
"""
P
y
t
h
o
n
"""

4. Python String Operations

4.1 Concatenation of two Python string characters

To concatenate two string characters in python, we use the ‘+’ operator:

Example

s1 = "Python"
s2 = "Programming"
# concatenation of s1 and s2
s = s1 + s2
print(s) # output: 'Python Programming'

4.2 Extract a substring

We extract a substring of a string s from the ith position up to the jth not included using the syntax:

substring = string[i:j]

Example

s = "Python"
substring = s[1:4]
print(substring) # output: 'yth'

5. The main methods associated with character strings in Python

The Python language is equipped with a large number of functions allowing the manipulation of string characters: calculation of the length of the string, transformation into upper and lower case, extracting a sub-string… Here is a non-exhaustive list:

Here is a non-exhaustive list:

s = "CRMEF OUJDA"
s = s.lower ()
print (s) # displays crmef oujda

s = "CRMEF OUJDA"
s = s.replace ("CRMEF", "ENS")
print (s) # display: ENS OUJDA

s = "CRMEF OUJDA"
n = len(s)
print ("the number of characters in the string s is:", n)
# displays the number of characters in the string s is: 11

name = "David"
age = 37
s = 'Hello, {}, you have {} ans'.format (name, age)
print (s) # display:  'Hello, David, you are 37'

s = "CRMEF OUJDA"
s1 = s [6: 9]
print (s1) # displays OUJ
s2 = s [6:]
print (s2) # displays OUJDA
s3 = s [: 4]
print (s3) # displays CRME