On Fri, Apr 5, 2019 at 5:34 AM Arup Rakshit <a...@zeit.io> wrote: > lines_of_words = [] > current_line_length = line_length > for word in words: > if current_line_length + len(word) > line_length: > lines_of_words.append([]) # new line > current_line_length = 0 > lines_of_words[-1].append(word) > current_line_length += len(word) > > My questions are: > > 1. why `line_length` is set to `current_line_length` initially? > 2. In the if clause why `current_line_length` is set back to 0 every time the > condition is true. > 3. Also why that `if` test is required there. >
I'll start with questions 2 and 3, then wheel back to #1. The 'current_line_length' variable is a classic running counter. It counts something until it hits a limit, then gets reset. Imagine emulating a vending machine - you add up the coins inserted until it reaches the value of the product, then dispense the product and reset the "money inserted" counter to zero. In this case, the word wrapping is done by saying "will this word fit? If not, go to a new line" for every word. So, to come back to question 1: The counter is initially full, rather than empty, to force the creation of a new line at the start of the loop. The very first word seen (since a "word" is guaranteed to have at least one character in it - text.split() makes sure of that) will be shown up as "nope, won't fit", so the list of lists gets its first value added to it. As an alternative, it could have been written like this: lines_of_words = [ [] ] # one initial line current_line_length = 0 # the initial line is empty Depending on the algorithm, sometimes it's easiest to force something to happen on the first iteration, and sometimes it's easiest to force it to happen at the end. (And sometimes both.) You'll see tricks like this in a lot of places. Hope that helps! :) ChrisA -- https://mail.python.org/mailman/listinfo/python-list
