On 2019-04-04 19:53, David Raymond wrote:
The function is constructing a list of the lines, which it will combine at the
end. Answering the questions in reverse order:
3. Also why that `if` test is required there.
The if statement is saying "I don't have room on my current line for the next word,
so time to start a new line"
2. In the if clause why `current_line_length` is set back to 0 every time the
condition is true.
current_line_length is, well, the length of the current line. Where it's set to 0 is when
you've just started a new line, so it's saying "I'm now on a new line and have used
up 0 characters so far on that line"
1. why `line_length` is set to `current_line_length` initially?
lines_of_words starts out empty. Setting current_line_length to line_length triggers the
"hey, I need to make a new line" on the first word, effectively creating the
first line.
Also, I feel like there's a bug in this, where
current_line_length += len(word)
should be...
current_line_length += (len(word) + 1)
Otherwise the line length doesn't count the spaces. And a lot of little words
will result in longer lines than you asked for.
Yep, spotted that too! :-) BTW, your fix also a bug: the last word on a
line won't be followed by a space (off-by-one). The easiest fix for that
is to add 1 to line_length initially, another little trick.
-----Original Message-----
From: Python-list
[mailto:python-list-bounces+david.raymond=tomtom....@python.org] On Behalf Of
Arup Rakshit
Sent: Thursday, April 04, 2019 2:33 PM
To: Python
Subject: I want understand how this word wrap program playing on input
I am reading a Python book, where the author used a simple word wrap program to
explain another concept. But I am not understanding some parts of the program.
def wrap(text, line_length):
"""Wrap a string to a specified line length"""
words = text.split()
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)
lines = [' '.join(line_of_words) for line_of_words in lines_of_words]
return '\n'.join(lines)
wealth_of_nations = "The annual labour of every nation is the fund which or" \
"iginally supplies it with all the necessaries and conveniencies of life
wh" \
"ich it annually consumes, and which consist always either in the
immediate" \
" produce of that labour, or in what is purchased with that produce from
ot" \
"her nations. According, therefore, as this produce, or what is purchased
w" \
"ith it, bears a greater or smaller proportion to the number of those who
a" \
"re to consume it, the nation will be better or worse supplied with all
the" \
" necessaries and conveniencies for which it has occasion."
Now when I call it:
python3 -i wrapper.py
>>> wrap(wealth_of_nations, 25)
'The annual labour of every\nnation is the fund which\noriginally supplies
it with\nall the necessaries and\nconveniencies of life which\nit annually
consumes, and\nwhich consist always either\nin the immediate produce of\nthat
labour, or in what is\npurchased with that produce\nfrom other
nations.\nAccording, therefore, as\nthis produce, or what is\npurchased with
it, bears a\ngreater or smaller\nproportion to the number of\nthose who are to
consume it,\nthe nation will be better or\nworse supplied with all
the\nnecessaries and\nconveniencies for which it\nhas occasion.'
>>> print(_)
The annual labour of every
nation is the fund which
originally supplies it with
all the necessaries and
conveniencies of life which
it annually consumes, and
which consist always either
in the immediate produce of
that labour, or in what is
purchased with that produce
from other nations.
According, therefore, as
this produce, or what is
purchased with it, bears a
greater or smaller
proportion to the number of
those who are to consume it,
the nation will be better or
worse supplied with all the
necessaries and
conveniencies for which it
has occasion.
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.
Can anyone help me to understand this program, I am totally confused.
Thanks,
Arup Rakshit
a...@zeit.io
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