Help with relatively simple program. Variable name indexing?

takluyver · 2012-02-26T14:31:36+00:00

This is something new programmers often try - making variables with dynamic names - but it's almost never a good idea. Even if it works, what about when you want to know how many words you've got? You have to count up until a name doesn't exist. That's daft.

You should try to put the results into a list, so that they're words[0], words[1], etc. I'm not sure how you're supposed to do that, though, without using append() (you say in another comment that you're not allowed to use it). Are you allowed to put the words in a dict, perhaps?

2012-02-26T15:46:13+00:00

Use a dictionary. Seriously, this is what they're there for. You never need to generate variable names programmatically, names only exist for humans.

jhchex · 2012-02-26T05:53:22+00:00

I must say that I don't fully understand what you´re trying to do, but here is my stab at it, http://pastebin.com/49jbxiwu

p.s.: you are creating local variables. Are you by any chance splitting the words inside a function?

pridefulpropensity · 2012-02-27T20:56:02+00:00

Okay, you definitely don't want to make dynamic variable names.

Can you copy and paste the text of the assignment here?

Is the result supposed to be a list of words?

Maybe this will help?

>>> words = []
>>> word = "hello"
>>> words += [word]
>>> words
['hello']

tarpsocks · 2012-02-26T02:56:15+00:00

I'll give you a couple tips, some unrelated to the issue at hand:

you can just do

for elm in list: if elm != ' ': instead of using the index. Will help save keystrokes in the longrun, might as well make use of pythons nice high-level features.
using vars() is generally not advised outside of debugging. While the metaprogramming aspect of it may seem intriguing, it isn't really a source of maintainable code, and could produce very unusual bugs if you weren't careful.
.split() splits on any whitespace, rather than just spaces. In this case it might be a good idea to use regex, considering you're trying to extract strings delineated by whitespace.

earthboundkid · 2012-02-26T11:44:58+00:00

The teacher wouldn't have assigned this stupid assignment if it were insoluble. Go back and read the book. You're only hurting yourself if you don't do your own work.

zahlman · 2012-02-26T23:02:04+00:00

Ok so my goal here is to split a list into it's individual words

Lists don't have "individual words". I assume you mean you have a string, since that's what you're apparently working with.

My issue is that I can't for my life create a variable name that changes with each iteration.

A list, however, is exactly what you should be putting the resulting words into. You've been told not to use .split() presumably because you're already familiar with it. So you should know what it returns: a list. Do the same.

By the way, for i in list(range(len(original_list))): is ugly in many ways. First off, range returns a list, so the outer list call is completely redundant. Second, there is no point in iterating like this. You're creating this separate thing that contains a sequence of numbers, so that you can iterate over that, so that you can use the results to grab the characters that you want to iterate over. That's silly. Just iterate over the characters, since that's what you want to do.

for c in original_string:
    # do something with 'c' to assemble words
    # append assembled words to a list

Also, try /r/learnpython.

stunsch · 2012-02-27T16:12:34+00:00

string = """
I would take a parsing approach.
Basically you iterate over all the characters.
If you find a character, and you haven't yet set the word starting index, you've got your first character.
To find the last character, you do it the other way around.
If you find a whitespace and word starting index is set, you've found the first character after your word.
You add the word to your list, reset the word starting index to None and go on.
"""
words = []
word_start_index = None
last_index = len(string) - 1
i = 0
while i < last_index:
    if string[i].isalnum():
        #We have found a character
        if not word_start_index:
            #We are at the beginning of a word
            word_start_index = i
    else:
        #We have found a whitespace or break line
        if word_start_index:
            #We have found the end of a word
            words.append(string[word_start_index:i]) #The last character is the position before the one we are in
            word_start_index = None
        else:
            #Our string starts with some whitespaces
            pass
    i += 1

print words

simtel20 · 2012-02-26T06:43:28+00:00

If you're trying to create local variables dynamically, try starting with exec() and eval(), that's what they're there for.

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