Incorrect claim in Example 1.29

Frank van Wijgerden — Mon, 25 Mar 2002 15:37:33 -0000

In section "1.12. Formatting strings", "Example 1.29.
String formatting vs. concatenating", points 3 and 4
claim that it is required to use:

>>> userCount = 6
>>> print "Users connected: %d" % (userCount, )
Users connected: 6

However, on my two Python systems (ActivePython 2.1.1
on win32, and Python 2.1 on linux2) I can also use the
following two alternatives:

>>> userCount = 6
>>> print "Users connected: %d" % (userCount)
Users connected: 6
>>> print "Users connected: %d" % userCount
Users connected: 6

To some extend, this contradicts the explanation given
in point 3 below the example: "(userCount, ) is a tuple
with one element. Yes, the syntax is a little strange,
but there's a good reason for it: it's unambiguously a
tuple. In fact, you can always include a comma after
the last element when defining a list, tuple, or
dictionary, but the comma is required when defining a
tuple with one element. If the comma weren't required,
Python wouldn't know whether (userCount) was a tuple
with one element or just the value of userCount."

Maybe it is something in Python 2.1 (and above?), but
the claim that "the comma is required when defining a
tuple with one element" is not true...

Hope this helps in improving "Dive Into Python", which
I really love as a jumpstarter into Python programming.

Frank

Recent changes to 1: Incorrect claim in Example 1.29

Incorrect claim in Example 1.29