On 02/22/2013 05:46 PM, Steven D'Aprano wrote:
On 23/02/13 08:26, Jim Byrnes wrote:
I am cleaning up my code and have a number of sqlite3 execute
statements that extend far past 80 characters.
From my reading implicit line joining with (), [] or {} seems to be
the preferred method, but
cur.execute('SELECT Account FROM pwds WHERE Category=? ORDER BY
Account COLLATE NOCASE', cat)
gives this error:
[...]
SyntaxError: EOL while scanning string literal
Single quote strings are limited to a single line, regardless of any
brackets (round, square or curly) around them. In this case, the
round brackets simply allow the arguments to cur.execute() to extend
over multiple lines, but each argument still has to obey the syntax
rules.
You can't expect this to work:
func(12345 67890) # ten digit number
just because of the parentheses. Neither do single-quote strings
suddenly gain the power to extend past the end of line.
But what you can do is use a line continuation \ as you have seen. Or
you can use a little-known feature of Python, implicit string
concatenation. The Python compiler will automatically concatenate
strings at compile-time:
s = "spam " 'ham ' 'eggs'
is a more-verbose way of writing:
s = "spam ham eggs"
Now obviously this example here is useless, but when combined with
parentheses, you get a powerful way of writing long strings:
cur.execute('SELECT Account FROM pwds' ' WHERE Category=?' ' ORDER BY
Account' ' COLLATE NOCASE', cat)
which I think is really nice to read. The best part is, because
these are string literals, the language promises to concatenate them
at compile-time, not runtime.
If implicit concatenation is too magical for you, you can use
explicit concatenation:
cur.execute('SELECT Account FROM pwds' + ' WHERE Category=?' + '
ORDER BY Account' + ' COLLATE NOCASE', cat)
At worst, the string concatenation + operator will apply at runtime,
which for a short string like this is not a big deal. But in
practice, I would expect Python's "keyhole optimizer" to see that it
is only string literals being concatenated, and perform
constant-folding at compile-time.
(Note: constant-folding is not a promise of the language. Not all
Python versions or implementations will do this.)
A fourth option is to use triple-quoted strings:
cur.execute('''SELECT Account FROM pwds WHERE Category=? ORDER BY
Account COLLATE NOCASE''', cat)
but this relies on your SQL database being happy to receive commands
with embedded newlines, which it may not be.
Thanks for giving me so many options to use in the future. When reading
I completely blew by the single quote on a single line part. The db is
sqlite3 and it seems happy with ''' strings.
Thanks, Jim
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
