meaning in python('+str(i)+')') code example

Example 1: str in python

#Strings or alphabets or -, +, *, /, ", :, ;, (, ) etc
#If there is a string then it means the value will be inside coates
a = 'Roger'
print(a, 'is my name')

Example 2: str(n)

for x in range(0,len(no)): 
			rotation = no[x:len(no)] + no[0:x]
			if not prime(int(rotation)) :
				return False    
	return True