Python string formatting fill value as variable [duplicate] - python-2.7

Question

This question already has answers here:
Format string dynamically [duplicate]
(5 answers)
Closed 8 years ago.
So I have this simple print statement:
print "%-10s %s" % ("test","string")
which prints the desired output:
test string
I'm trying to figure out the correct syntax for a case where the fill value is a variable. Example:
w = 10
print "%-s %s" % (w,"test","string")
So %-s should be replaced with what to accommodate the fill value?
If I remember it correctly, the syntax is similar to %-xs where x is replaced by a an int variable. I might be mistaken though.
Note
I know this question is probably duplicated since this is really elementary string formatting issue. However, after some time of searching for the right syntax I gave up.

Answer 1

I would be inclined to use str.format, instead:
>>> print "{:{width}}{}".format("test", "string", width=10)
test string

Answer 2

You could do this in two stages: First, create the proper format string, then use it to create the actual output. Use %d as a placeholder for the width and escape each other % as %%.
formatstring = "%%-%ds %%s" % w
print formatstring % ("test","string")
Or in one line:
print ("%%-%ds %%s" % w) % ("test","string")
Update: As pointed out by Martijn in the comments, you can also use * in the format string:
print "%-*s %s" % (w,"test","string")
From the documentation:
Minimum field width (optional). If specified as an '*' (asterisk), the actual width is read from the next element of the tuple in values, and the object to convert comes after the minimum field width and optional precision.