Answers for "python for loop from end to start"

4

reverse for loop python

# 1.
for i in reversed(range(3)): # output: 	0
    print(i)				 #			1
    						 # 			2
# works with arrays as well , reversed(arr)

# 2.
# another alternative is
arr = [1,2,3]
# note: arr[start : end : step]
for i in arr[::-1]:			 # output:	0
  print(i)					 # 			1
  							 #			2

# 3.
# last alternative i don't recommened!
# note: range(start, end, step)
for i in range(len(arr) - 1, -1 , -1): 	# output: 	0
  print(i)								# 			1
  										# 			2
# read more on range() to understand even better how it works has the same rules as the arrays
Posted by: Guest on June-08-2020
2

python iterate backwards through list

>>> a = ["foo", "bar", "baz"]
>>> for i in reversed(a):
...     print(i)
... 

or

>>> for i, e in reversed(list(enumerate(a))):
...     print(i, e)
Posted by: Guest on December-03-2019
2

python loop back to start

def main(): #defines the area in indents that will be triggered with main()#
  print('hi')
  yn = input('Wanna loop back to the start? ')
  if yn = 'yes':
    main() #loops back to where we defined main#
    
main() #This starts the main loop, without this, main would just be defined but not run#
Posted by: Guest on August-09-2020
7

python for loop start, end

my_list = [1, 2, 3]
my_list.reverse()           # my_list is modified
print(my_list)              # '[3, 2, 1]'
my_revert = my_list[::-1]   # my_list stays [3, 2, 1]
print(my_revert)            # '[1, 2, 3]'
# Item by item reverse with range(<start>, <end>, <step>)
for i in range(len(my_list), 0, -1):		# my_list is [3, 2, 1]
    print(my_list[i-1])		# '1' '2' '3'
for i in reversed(range(len(my_list))):
    print(my_list[i])       # '1' '2' '3'
Posted by: Guest on May-15-2021

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