Question

I am new to python and would appreciate a little help.

How does one do the following:

1. Having converted each line within a file to a nested list,
   e.g. [['line 1', 'a'], ['line 2','b']] how do I flatten the list so that each line is associated with a variable. Assume that the first member in each list, i.e. i[:][0], is known.

2. Is it possible to associate more than one list with one variable, i.e. can x = [list1], [list2]?

3. Having used a for loop on a list, how those one associate aspects of that list with a variable? See example below.

Example:

for i in list_1:
    if i[:][0] == 'm':
        i[2] = a
        i[3] = b
        i[4] = c

The above returns NameError, a, b, c, not defined. How does one define variables resulting from iterations in a for loop or loops in general?

Hope I was clear and succinct as I am perplexed!

Update:

To clarify:

I have a nested list, where each list within the nest holds strings. These strings are actually numbers. I wish to convert the strings to integers in order to perform arithmetic operations.

Example:

[['1', '2', '3'], ['4', '5', '6'], ['7', '8', '9']]

Now, to convert each string to an integer, is abs() appropriate? How should this be implemented?

Also, to sum the third item of each list within the nest and assign the total to a variable? Should I define a function for this?

Any suggestions on how to deal with this are much appreciated!

Also, the earlier suggestions, made me realise that my thinking was creating the problem! Thanks!

Answer 1

# Answer to question 1 - just use the built-in functionality of lists.
#
# There is no need to use variables when lists let you do so much more
#   in a quick and organised fashion.
lines = []
for line in open_file:
   lines.append(line)

Since Li0liQ already answered questions 2 and 3, I’d just like to add a recommendation regarding question 3. You really don’t need to make a copy of the list via i[:] since you’re just testing a value in the list.