[Tutor] Enter mode where you can input list indices

[Alan Gauld]

On 16/10/2021 16:20, Julius Hamilton wrote:
> Hey,
> 
> I would like to explore the contents of a list where I could just enter a
> mode where any index I type in, it would print the value for some list,
> like this:
> 
>>>> p()
> 1
> ["apple", "cat"]
> 1 2
> cat
> 3
> Index out of bounds

You might want to look at the cmd module which provides a
framework for building interpreter like prompts into your program.

> def p():
>   n = input()

n is probably a bad name. index_str or similar
would be more descriptive.

>   while n != "":
> 
> After the input is received it must be parsed into a list of integers:
>     n = n.split(' ')
>     indices = []
>       for item in n:
>         indices.append(int(item))

This is basically a list comprehension:

indices = [int(item) for item in n]

> indices. Next, index the list (in the enclosing scope) by however many
> indices there are:
> 
>     for i in indices:
>       list = list[i]

This is the more challenging part, you probably want
to pass the list into the function. Or if you want to
use a different list for each iteration you would pass
a list of lists. In that ase your input() should
include a prompt describing which list is to be indexed.
Something like:

lists=(("list1",lst1),("list2",lst2,....)

def p(lists):
   for List in lists:
      index_str = input("type  list of indices for %s"%List[0]
      while index_str != "":
        ...
        for n in indices:
          print(List[1][n]
        ...
-- 
Alan G
Author of the Learn to Program web site
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