How to gracefully break up a long string

Question

Look, I have seen many of the answers provided on this site that deal with aspects of my question. The [aforementioned] answers usually provide already existing examples that are too basic to be helpful--at least for me. But hey, maybe I'm over-complicating it.

Here is the original long-line:

    for i in range(2, l + 1):
        job_count_array["//form[@id='SubAvailSelectForm']/font/table[2]/tbody/tr[%d]/td[1]/small" % i] = sel.get_text("//form[@id='SubAvailSelectForm']/font/table[2]/tbody/tr[%d]/td[1]/small" % i)

Here is my attempt at implementing the 'long-line continuation' etiquette (as outlined by a pycon handout from 2007 that I found here):

    for i in range(2, l + 1):
        job_count_array["//form[@id='SubAvailSelectForm']/font/table[2]/ \
                        tbody/tr[%d]/td[1]/small" % i] = sel.get_text("/ \
                        /form[@id='SubAvailSelectForm']/font/table[2]/tb \
                        ody/tr[%d]/td[1]/small" % i)

Will my attempt (a) be interpreted correctly by the parser and/or (b) be made any more 'pretty' or efficient by any helpful contributers? Thank you.

sberry · Accepted Answer · 2013-12-04T05:31:43.897

I would go with either of the following two choices:

for i in range(2, l + 1):
    replace_index = "//form[@id='SubAvailSelectForm']/font/table[2]/tbody/tr[%d]/td[1]/small" % (i,)
    job_count_array[replace_index] = sel.get_text(replace_index)

Firstly, you have the same long string used twice, so use replace_index in its place. This makes the code shorter, and guarantees you don't have any small, hard-to-spot typos differing between the two.

for i in range(2, l + 1):
    replace_index = ("//form[@id='SubAvailSelectForm']/"
                     "font/table[2]/tbody/tr[%d]/td[1]/small") % (i,)
    job_count_array[replace_index] = sel.get_text(replace_index)

Second, you can use the "automatic concatenation of strings inside parentheses" trick instead of the end of line escaping for strings. I find it much easier to read this way.

Also worth noting is using (%i,) instead of %i for the string formatting. It has proven beneficial in my past to set up a single string formatting argument into a tuple so it is easier to add additional arguments in the future, plus it is nice to be consistent in how string formatting arguments are presented.

Concenating strings instead of using one long one spanned across several lines also avoids a potential bug - the long string *includes* all of the white space used to line up each line with the first (just not the newlines, unless you use a triple quoted string instead of escapes), while the concatenated one has the same contents as if you put it all on one line. — lvc, Dec 04 '13 at 05:25
I find the new format syntax also helps with keeping lines neat. `foo = 'hello world {}'` then later on `print(foo.format(42))` — Burhan Khalid, Dec 04 '13 at 05:35

How to gracefully break up a long string

1 Answers1