String .format() vs. % formatting with Unicode data

Question

With

print("    {:d}). {:s} ({:d})".format(i, account, num_char))

I get the error:

UnicodeEncodeError: 'ascii' codec can't encode character u'\xe9' in position 4: ordinal not in range(128)

but when I change it to:

print "    %d). %s (%d)" % (i, account, num_char)

then there are no problem and output is identical with both prints.

So what is wrong in the first expression and why does it work in the second?

Answer 1

In the first example, you are calling the format method of str object passing unicode arguments. This causes an error. You should use

print(u"    {:d}). {:s} ({:d})".format(i, account, num_char))

instead.

In the second one, you are using the % operator which automatically returns unicode when either format or object is unicode. From the docs:

6. If the object or format provided is a unicode string, the resulting string will also be unicode.