python add to a string

# Concatenation
string1 = "str"
string2 = "ing"
string3 = string1 + string2
# string3 is str + ing which is 'string'
# OR
print(string1 + string2)            # prints 'string' 

# Format
string3 = f"{string1}{string2}"     # prints 'string'

# initializing string  
test_string = "GFG"
  
# initializing add_string 
add_string = " is best"
  
# printing original string  
print("The original string : " + str(test_string)) 
  
# printing original add string  
print("The add string : " + str(add_string)) 
  
# Using += operator 
# adding one string to another  
test_string += add_string 

def add_Is(op):
  if len(op) >= 2 and op[:2] == 'Is':
    return op
  return 'Is' + op
print(add_Is('Ho'))

>>> orig_string = 'Hello'
>>> orig_string + ', world'
'Hello, world'
>>> orig_string
'Hello'
>>> full_sentence = orig_string + ', world'
>>> full_sentence
'Hello, world'