concardinate str and a variable in python

print("the number is five " + str(5)) 

# 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 

my_list = ['a', 'b', 'c', 'd']
my_string = ','.join(my_list)
# Output = 'a,b,c,d'