How can I create python strings with placeholders with arbitrary number of elements

Question

I can do

string="%s"*3
print string %(var1,var2,var3)

but I can't get the vars into another variable so that I can create a list of vars on the fly with app logic. for example

if condition:
  add a new %s to string variable
  vars.append(newvar)

else:
  remove one %s from string
  vars.pop()
print string with placeholders

Any ideas on how to do this with python 2.6 ?

Answer 1

How about this?

print ("%s" * len(vars)) % tuple(vars)

Really though, that's a rather silly way to do things. If you just want to squish all the variables together in one big string, this is likely a better idea:

print ''.join(str(x) for x in vars)

That does require at least Python 2.4 to work.

Answer 2

use a list to append/remove strings then "".join(yourlist) before printing

>>> q = []
>>> for x in range(3):
    q.append("%s")
>>> "".join(q)
'%s%s%s'
>>> print "".join(q) % ("a","b","c")
abc

Answer 3

n = 0
if condition:
  increment n
  vars.append(newvar)

else:
  decrement n
  vars.pop()

string = "%s" * n
print string with placeholders

But you don't really need string formatting if you're just joining the vars; why not do:

"".join( map( str, vars ) )