While loops and negative list indexing in python

Question

Please help me understand while loops and negative indexing in lists in python.

Answer 1

Code ,

both of your *mentioned topics* are covered also by sololearn tutorials. for better understanding it is recommended to learn from these lessons. also it is crucial to do some execises to get a better understanding for using negative indexing or a mix of positive and negative indexing.

> while loops
tutorial: introduction to python
module: control flow
lesson: while loops

> negative indexing:
tutorial: python developer
module: working with lists
lesson: indexing, using indexing, slicing, using slicing, advanced slicing and indexing.

Answer 2

while loops are a type of loop that keeps running as long as a condition set is true. For example:

count = 0
while count < 5:
print(count)
count += 1

This loop's condition is "count < 5", and the loop adds 1 to the count after every iteration. So after running 5 times and printing 0 1 2 3 4, the count reaches 5(and the condition becomes false as 5 is not less than 5, 5==5) and thus the loop stops. Remember to include a counter or another mechanism to make the condition false at some point, if you don't want infinite loop.

Negative indexing allows you to extract items from the end of a list. Let's take this list as an example:
colors = ["red", "green", "blue", "orange", "yellow"]

When we use negative indexing, we decrease the index(so in negative term, -1 to -2 to -3 is decreasing) to go from the right(end) to the left(start) of a list. If we do:
print(colors[-1])

This will output the item which is at the end of the list(yellow). If you use -2, it'll print orange, as it goes from right to left.

Answer 3

While loops? It's used to iterate (repeat) a specifical block of code as long as the condition is true, e.g:

I = 34
while I > 0:
print ("yes")
I--

As for negative indexing, it's used to call a parts of the last strings in a list or word