Question

PYTHON

The first function you will write should be called ‘countDown’. Your function should take zero (0) arguments. The function should return one (1) list containing integers from 10 to 1 and finally, the string “Liftoff!”. (i.e., [10, 9, 8, 7, 6, 5, 4, 3, 2, 1, ‘Liftoff!’]). You function must be recursive (i.e., it should contain a call to itself within the function body). You will get NO credit if you use any loops (for, while, etc).

3. Function One: countDown The first function you will write should be called 'count own Your function should take zero (0) arguments The function should return one (1) list containing integers from 10 to 1 and finally, the string "Liftoff!". (i.e. to You function must be recursive (i.e., it should contain a call to itself within the function body). You will get NO credit if you use any loops (for, while, etc).

Answer 1

For a recursive function to be executed properly, there should be one criteria to stop the recursion called base case. If base case is not presion, recursion will go on infinitely

There are two ways to hold the base case without passing it into parameter.

1) passing optional parameter. : - Here parameter is passed but is optional. i.e. while calling method, we dont need to specify is

the code is as below: -

def countDown(n=10):
    if n == 0:
        return ['Liftoff!']
    else:
        return [n] + countDown(n-1)

print(countDown())

2. By accessing some global variable

Here we use some declared global variable to create a base case. The code is as below

n = 11

def countDown():

global n

n = n - 1

if n == 0:

return ['Liftoff!']

else:

return [n] + countDown()

print(countDown())

3. Using method variables

def countDown():
countDown.counter = countDown.counter - 1
if countDown.counter == 0:
return ['Liftoff!']
else:
return [countDown.counter] + countDown()
countDown.counter = 11
print(countDown())

main.py def countDown (): [10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 'Liftoff!'] countDown . counter countDown counter - 1 if countDown.counter0: return ['Liftoff!'] else: return [countDown.counter] countDown.counter 11 print (countDown O) countDown ()

4. Using helper function

def countDown():
return countDownHelper(10)
  
def countDownHelper(num):
if num == 0:
return ['Liftoff!']
else:
return [num] + countDownHelper(num-1)

print(countDown())

main.py - def countDown (): [10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 'Liftoff!'] return countDownHelper (10) def countDownHelper(num): if num: return ['Liftoff!'] else: return [num] countDownHelper(num-1) print(countDown))

Note:- Without base case we cannot define any recursion. Please comment if you have any query on this.