Downsides to reading strings from Excel in python using encode('utf-8')

Question

I am reading a large amount of data from an excel spreadsheet in which I read (and reformat and rewrite) from the spreadsheet using the following general structure:

book = open_workbook('file.xls')
sheettwo = book.sheet_by_index(1)
out = open('output.file', 'w')
for i in range(sheettwo.nrows):
     z = i + 1
     toprint = """formatting of the data im writing. important stuff is to the right -> """ + str(sheettwo.cell(z,y).value) + """ more formatting! """ + str(sheettwo.cell(z,x).value.encode('utf-8')) + """ and done"""
     out.write(toprint)
     out.write("\n")

where x and y are arbitrary cells in this case, with x being less arbitrary and containing utf-8 characters

So far I have only been using the .encode('utf-8') in cells where I know there will be errors otherwise or foresee an error without using utf-8.

My question is basically this: is there a disadvantage to using .encode('utf-8') on all of the cells even if it is unnecessary? Efficiency is not an issue. the main issue is that it works even if there is a utf-8 character in a place there shouldn't be. If no errors would occur if I just lump the ".encode('utf-8')" onto every cell read, I will probably end up doing that.

Answer 1

The XLRD Documentation states it clearly: "From Excel 97 onwards, text in Excel spreadsheets has been stored as Unicode.". Since you are likely reading in files newer than 97, they are containing Unicode codepoints anyway. It is therefore necessary that keep the content of these cells as Unicode within Python and do not convert them to ASCII (which you do in with the str() function). Use this code below:

book = open_workbook('file.xls')
sheettwo = book.sheet_by_index(1)
#Make sure your writing Unicode encoded in UTF-8
out = open('output.file', 'w')
for i in range(sheettwo.nrows):
    z = i + 1
    toprint = u"formatting of the data im writing. important stuff is to the right -> " + unicode(sheettwo.cell(z,y).value) + u" more formatting! " + unicode(sheettwo.cell(z,x).value) + u" and done\n"
    out.write(toprint.encode('UTF-8'))

Answer 2

This answer is really a few mild comments on the accepted answer, but they need better formatting than the SO comment facility provides.

(1) Avoiding the SO horizontal scrollbar enhances the chance that people will read your code. Try wrapping your lines, for example:

toprint = u"".join([
    u"formatting of the data im writing. "
    u"important stuff is to the right -> ",
    unicode(sheettwo.cell(z,y).value),
    u" more formatting! ",
    unicode(sheettwo.cell(z,x).value),
    u" and done\n"
    ])
out.write(toprint.encode('UTF-8'))

(2) Presumably you are using unicode() to convert floats and ints to unicode; it does nothing for values that are already unicode. Be aware that unicode(), like str(), gives you only 12 digits of precision for floats:

>>> unicode(123456.78901234567)
u'123456.789012'

If that is a bother, you might like to try something like this:

>>> def full_precision(x):
>>> ... return unicode(repr(x) if isinstance(x, float) else x)
>>> ...
>>> full_precision(u'\u0400')
u'\u0400'
>>> full_precision(1234)
u'1234'
>>> full_precision(123456.78901234567)
u'123456.78901234567'

(3) xlrd builds Cell objects on the fly when demanded.

sheettwo.cell(z,y).value # slower
sheettwo.cell_value(z,y) # faster