Question about tuple lengths

[Carl J. Van Arsdall]

From my interpreter prompt:
1

So why is a tuple containing the string "blah" without the comma of
length four? Is there a good reason for this or is this a bug?

--

Carl J. Van Arsdall
(e-mail address removed)
Build and Release
MontaVista Software

 

[MM Zeeman]

From my interpreter prompt:

1

So why is a tuple containing the string "blah" without the comma of
length four? Is there a good reason for this or is this a bug?

Hello,

Thats because the expression ("blah") actually resolves to "blah" instead of
a tuple containing the string "blah".
<type 'str'>

Adding a comma after spam results in the tuple being created.
<type 'tuple'>

And to make things even more confusing, just adding a comma without braces
will give you a tuple too.
('spam',)

The explanation for this all can be found at:
http://docs.python.org/ref/parenthesized.html

Regards,

Maas

 

[Steven D'Aprano]

From my interpreter prompt:

There is a special place in Hell reserved for people who overwrite
built-in functions like tuple(), list(), str() and so forth. *wink*

4

Brackets on their own are just used for grouping, so ("blah") is the same
as just "blah", namely a string with four characters.

The only exception to this is the empty tuple, which is made with an empty ().

1

Tuples are made with commas, not brackets. You could write just "blah",
without the brackets and it would still work.

py> t = "blah",
py> t
('blah',)

So why is a tuple containing the string "blah" without the comma of
length four? Is there a good reason for this or is this a bug?

It's not a bug.

 

[Larry Bates]

From my interpreter prompt:

1

So why is a tuple containing the string "blah" without the comma of
length four? Is there a good reason for this or is this a bug?

Additional note:

You should not give a tuple a variable name of tuple, it masks
the built-in tuple() function. This also goes for str, or other
built-ins. This will "bite" you at some point if it hasn't already.

-Larry Bates