Basic calculator program in Python

I was writing a basic calculator program to practice my skills at python.
I'm a beginner at Python and was wondering if there is a way to simplify this code of mine? It seems a little bit too long and messy in some sort of way.
Again, I'm still a beginner so I don't know all the tricks in the book!

```
import math
import time

def add(x,y):
return x + y

def subtract(x,y):
return x - y

def divide(x,y):
return x / y

def multiply(x,y):
return x * y

def sqrt(x):
if math.sqrt(x) * math.sqrt(x):
return False
else:
return math.sqrt(x)

def power(x,y):
return math.pow(x,y)

def repeat():
print('Would you like to perform another calculation? y/n')
rep = input('')
if rep.lower() == 'y':
time.sleep(0.5)
main()
elif rep.lower() == 'n':
print('Goodbye!')
time.sleep(1)
exit()
else:
print('Please enter y/n.')
time.sleep(1)
repeat()

def numCheck(x):
try:
int(x)
except ValueError:
print("Please enter a valid number.")
print('')
time.sleep(1)
main()

def choiceCheck(y, z):
for x in y:
if x == z:
return True
break
else:
pass

def main():
choices = ['1', '2', '3', '4']
print('Choose your operation: ')
print('1. Add')
print('2. Subtract')
print('3. Divide')
print('4. Multiply')
print('5. Square Root')
print('6. Exponent')
print('1/2/3/4/5/6')
choice = input('')
if choice == '5':
print('Please choose the number you would like to square root.')
rt = input('')
numCheck(rt)
rt = int(rt)
rts = sqrt(rt)
if rts == False:
print('%d is an irrational number.' % (rt))
else:
print('The square root of %d is %d' % (rt, rts))
repeat()
elif choice == '6':
print('Choose the number you would like to raise to a power: ')
base = input('')
numCheck(base)
base = int(base)
print('')
print('Now please choose the indice: ')
ind = i

This being Python, where indentation is significant, it is important to consistently follow the convention of four spaces per level.

You shouldn't format the square root as %d, since the result is rarely an integer.

There are several recommendations that I could make about organizing this code, but the single most important point is that functions should not be treated as goto labels. If you need a loop, then write a loop using while or for. Don't have main call main(). Don't have repeat call main(). Don't have repeat call repeat(). Otherwise, you end up with spaghetti code.

StackExchange Code Review Q#142851, answer score: 5