Example 1: 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
Example 2: python range reverse
When you call range() with three arguments, you can choose not only
where the series of numbers will start and stop but also how big the
difference will be between one number and the next.
range(start, stop, step)
If your 'step' is negative and 'start' is bigger than 'stop', then
you move through a series of decreasing numbers.
for i in range(10,0,-1):
print(i, end=' ')
# Output: 10 9 8 7 6 5 4 3 2 1
Example 3: python reverse range
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'
Example 4: reverse a number in python
# Python string/number reverser
example_number = 12143
example_string = "Hello there"
def reverse(thing):
thing = str(thing) # convert it to a string, just in case it was a number
list_of_chars = [char for char in thing]
reversed_list_of_chars = []
x = -1
for char in list_of_chars:
reversed_list_of_chars.append(list_of_chars[x])
x += -1
reversed_thing = ''.join(reversed_list_of_chars)
return reversed_thing
# Or alternatively do:
print(reversed_thing)
# Run it by doing this
reverse(example_number)
reverse(example_string)
Example 5: reversed(range
>>> type(range(3))
<class 'range'>
Example 6: how does the range function work in python when counting down
range(4)
#considers numbers 0,1,2,3
range(1, 4)
#considers numbers 1,2,3
range(1, 4, 2)
#considers numbers 1,3
range(4, 1, -1)
#considers numbers 4,3,2