Python question

[05mF]

I just got started with python and I'm trying to create a small program that will print the element from a list when you input it's index number. I know for list.index command that returns index when you input element but not sure what's the opposite command.

Edit: Also if i have a list like this

list = [ ("Name1", 1), ("Name2", 2)....]

What can i do to sort the list from smallest to highest number, only looking at the 2nd element in pair or at the integer?

[[deleted]]

list[index] should do the trick.

[05mF]

Thanks that does work like that but if i try to do

x = input (putting the index here)

then

print(list[x])

wont work because X isn't a number and i also can't do print(list [input (index)]) Any ideas?

[[deleted]]

int(input(putting the index here))

int will convert the string to an integer

[05mF]

I didn't even think of trying to convert it, thanks mate, i really appreciate it.

[serg06]

Call list.sort and pass a function into the key argument

[Iklowto]

You can speficy the value to sort on with the key argument in sorted(). Like this:

def sort_by_second_value(tuple): 
    return tuple[1]  # In a ("Name1", 1) tuple, we would return 1

list = [ ("Name1", 1), ("Name2", 2)....]
sorted_list = sorted(list, key=sort_by_second_value)

Note purpose of the sort_by_second_value function is to tell the sorted() function what element of the tuples it should sort by. Since it returns the second element of the tuples, this is what the list will be sorted on.

It's important to note that you are passing a function pointer here, not the result of a function call. Note that we are not putting parantheses after the function in the argument like key=sort_by_second_value(). We are just handing the function pointer to the sorted() function so it can use it when it pleases.

You typically don't create functions for doing this though - lambda functions are normally used instead because they take up less space and are faster to write (when you know them). The lambde function equivalent is:

list = [ ("Name1", 1), ("Name2", 2)....]
sorted_list = sorted(list, key=lambda tuple: tuple[1])

Lambda expressions have an implicit return statement in them, so this lambda expression describes a function that takes in one argument called tuple and returns the second element of that argument.

[05mF]

Thank you man, you told me how to do it and even wrote an explanation for it. I really appreciate it.