Python Bubble sort code

Question

I have written the below bubble sort code in Python.

def bubble_sort():
 num_list=[]
 list_cnt=input("How many numbers you would like to sort:")
 for i in range(int(list_cnt)): ### need to convert the value returned by input()
 num_list.append(input("Enter " +str(i)+" number:")) ##here we are using append method of list
 print("The values input are as follows:")
 print(num_list)
 print(len(num_list))
 ### Below new line of code added to convert list to integer###
 num_list=list(map(int,num_list))
 ## with the above line the code is now working as expected##
 max_index=len(num_list)-1 ## because list begins with 0
 print("max_index is:",max_index)
 for i in range(len(num_list)-1):
 j=0
 swapped=False
 for j in range(len(num_list)-1):
 if num_list[j] > num_list[j+1]:
 num_list[j],num_list[j+1]=num_list[j+1],num_list[j]
 print("Sorted when j=" +str(j)+ " and i=" + str(i)+ " is:\n ")
 print(num_list)
 swapped=True
 if not swapped:
 break
 print("The sorted list is :")
 print(num_list) 
bubble_sort()

Answer 1

Your code's quite good. I'd however change it in the following ways:

1. Move the creation of the lits out of the buble_sort.
2. Remove the prints from buble_sort.
3. Follow PEP8.
4. Change for i in range(...) to while True:.
5. Use better variables. num_list to array could do.
6. Use str.format, rather than string addition.
7. Change the creation of num_list to use a list comprehension.

def bubble_sort(array):
 while True:
 swapped = False
 for j in range(len(array)-1):
 if array[j] > array[j+1]:
 array[j], array[j+1] = array[j+1], array[j]
 swapped = True
 if not swapped:
 break
if __name__ == '__main__':
 amount = input("How many numbers you would like to sort:")
 array = [
 int(input("Enter {} number:".format(i)))
 for i in range(int(amount))
 ]
 print("The values input are as follows: {}".format(array))
 bubble_sort(array)
 print("The sorted list is: {}".format(array))

• Raimund Krämer: I agree with everything except renaming num_list to array, since it is a list, not an array. numbers would probably be better, since it explains what it contains, and implies that it is a sequence without stating a concrete type.
• Peilonrayz: @RaimundKrämer You could use list however that shadows list. They're also IIRC arrays with list interfaces, so it's simpler to call it a list. Also we're only using it for it's array interface. But yeah numbers could work.

Answer 2

The IO code is mixed with the logic code. I separated them. Also, I made a few other changes including removing useless comments (the code should speak for itself, your comments don't add much; if you need comments, that probably means you should simplify your code). I also converted the numbers as soon as they are input.

def bubble_sort(num_list):
 for i in range(len(num_list)-1):
 swapped = False
 
 for j in range(len(num_list) - 1):
 if num_list[j] > num_list[j+1]:
 num_list[j], num_list[j+1] = num_list[j+1], num_list[j]
 swapped = True
 
 if not swapped:
 return
def main():
 num_list = []
 num_items = int(input("How many numbers you would like to sort:"))
 
 for i in range(num_items):
 num_list.append(int(input("Enter " + str(i + 1) + "st number:")))
 
 bubble_sort(num_list)
 print("The sorted list is:")
 print(num_list)
if __name__ == '__main__':
 main()