a question

[Nader Emami]

L.S.,

I have a long command in Unix and I have to use os.system(cmd)
statement. I do the following:

cmd = '%s/mos user wmarch, cd /fa/wm/%s/%s, mkdir %s, put %s, chmod 644
%s' % (mosbin, jaar, filetype, filetype)
status = os.system(cmd)


This is not very clear, and I have to break this long line in two
segment by means of the next character '\' :
cmd = '%s/mos user wmarch, cd /fa/wm/%s/%s, mkdir %s, put %s, \
chmod 644 %s' % (mosbin, jaar, filetype, filetype)

But in this case I get a syntax error! I don't know how I can solve this
problem. Could somebody tell me about this?

With regards,
Nader


(this

 

[Steve Holden]

L.S.,

I have a long command in Unix and I have to use os.system(cmd)
statement. I do the following:

cmd = '%s/mos user wmarch, cd /fa/wm/%s/%s, mkdir %s, put %s, chmod 644
%s' % (mosbin, jaar, filetype, filetype)
status = os.system(cmd)


This is not very clear, and I have to break this long line in two
segment by means of the next character '\' :
cmd = '%s/mos user wmarch, cd /fa/wm/%s/%s, mkdir %s, put %s, \
chmod 644 %s' % (mosbin, jaar, filetype, filetype)

But in this case I get a syntax error! I don't know how I can solve this
problem. Could somebody tell me about this?

The error you get is NOT a syntax error:

The interpreter is probably complaining because it needs six values to
fill out the format and you only provided four.

In future, by the way, always include the error message in such posts!

regards
Steve

 

[Andrew Koenig]

The error you get is NOT a syntax error:


The interpreter is probably complaining because it needs six values to
fill out the format and you only provided four.

Also, I'm dubious about the idea of splitting a string literal across
multiple lines, as it's impossible to indent such a literal nicely without
putting stray spaces into its contents. So instead of writing

'this is a\
long string'

and not making it clear how many spaces you intend between 'a' and 'long',
how about writing this instead?

('this is a '
'long string')

in which the contents are not in doubt. This code takes advantage of two
properties of Python:

1) Multiple string literals with only whitespace between them are
automatically concatenated;

2) Ending a line inside unbalanced parentheses implicitly makes the next
line part of the same statement.

 

[Will Stuyvesant]

how about writing this instead?

('this is a '
'long string')

Yes, nice. And to make that possible we have to write
('one-string-item',) instead of ('one-string-item') if we want a tuple
with one string inside. Sometimes that feels like a wart to me, but
now I know it, sometimes not.

 

[Steve Holden]

Yes, nice. And to make that possible we have to write
('one-string-item',) instead of ('one-string-item') if we want a tuple
with one string inside. Sometimes that feels like a wart to me, but
now I know it, sometimes not.

That has very little to do with tuples. You could just as easily write

'this is a '\
'long string'

It's the dangling comma that's required to specify a tuple:

regards
Steve

 

[Bill Mill]

Nader,

You've got a couple problems. First, you need to end the string before
putting a continuation in. Secondly, you have 6 variables to be
substituted and only provide 4. Here's some code, edited to show how
to use continutations to join strings:
'1/mos user wmarch, cd /fa/wm/1/1, mkdir 1, put 1, chmod 6441'

Peace
Bill Mill
bill.mill at gmail.com

 

[Paul McGuire]

Yes, nice. And to make that possible we have to write
('one-string-item',) instead of ('one-string-item') if we want a tuple
with one string inside. Sometimes that feels like a wart to me, but
now I know it, sometimes not.

I don't think the goal was to have a tuple with a single string in it. The
poster said he was taking advantage of two features of Python:

"1) Multiple string literals with only whitespace between them are
automatically concatenated;

2) Ending a line inside unbalanced parentheses implicitly makes the next
line part of the same statement."

The parens are there just to avoid using the '\' continuation character.

-- Paul

 

[Fredrik Lundh]

You've got a couple problems. First, you need to end the string before
putting a continuation in.

.... pe"
'nope'
File "<stdin>", line 1
"however\
^
SyntaxError: EOL while scanning single-quoted string

(in the second case, the ^ is trying to point out that I added
some whitespace after the backslash)

</F>

 

[Bill Mill]

You are correct, sir. Didn't know you could do that. Neato.

Peace
Bill Mill
bill.mill at gmail.com