In this article, we’ll be covering about Strings in Python.
Strings in Python are a sequence of characters enclosed in single-quotes, double-quotes or sometimes in triple-quotes.

string = "Hello World"
print(type(string))

Output:

<class 'str'>

Accessing characters in String: We can access characters in the string by using an index number in the square brackets.

string = "Hello World"

print(string[0])

print(string[4])

Output:

H
o

Iterating through String: We can use both for and while loop to iterate through a string.

string = "Hello World"
print("Iterating through string using for loop")
# for loop
for i in string:

  print(i)

print("Iterating through string using while loop")
# while loop
j = 0
while j < len(string):
  print(string[j])
  j += 1
   

Output:

print("Iterating through string using for loop")
H
e
l
l
o
 
W
o
r
l
d
print("Iterating through string using while loop")
H
e
l
l
o
 
W
o
r
l
d

Deleting a character: We cannot delete or remove any character from the string as they are immutable. But we can delete the entire string using del keyword/function.

string = "Hello World"
del string
# del(string), both syntax work
print(string)

Output:

Traceback (most recent call last):
  File "C:\Users\user\AppData\Local\Programs\Python\Python36\all_prgm\biochemithon articles\testing bioc.py", line 3, in 
    print(string)
NameError: name 'string' is not defined

Concatenation of two or more Strings: Joining two or more strings into a single string is called concatenation.
We can either use ‘+’ operator or f-string to join strings.

string1 = "Hello"
string2 = "World"
print("string concatenation using \
'+' operator:\n",string1 + string2)
print("string concatenation using \
'f-string':\n",f'{string1}{string2}')

Output:

string concatenation using '+' operator:
 HelloWorld
string concatenation using 'f-string':
 HelloWorld

We can also use ‘*’ operator to repeat the string for a given number of times.

string = "Hello"
print(string * 5)

Output:

HelloHelloHelloHelloHello

Slicing: It is used to return a part of the string. We need to specify the starting index (optional) and the ending index, separated by a colon.

string = "Hello World"
print(string[2 : 6])

Output:

llo

We can also use negative index to slice string from the end.

string = "Hello World"
print(string[-5 : -2])

Output:

Wor

Length of String: We can use len() function to find out the length of the string.

string = "Hello World"
print(len(string))

Output:

11

String Membership test: To check if a substring exist in the string or not we use ‘in’ keyword.

print("ello" in "Hello World")

print("ab" in "Hello World")

Output:

True
False