Insert variable values into a string

data = self.cmd("r.out.gdal in=rdata out=geo{0}.tif".format(i))
self.dataOutTIF.setValue("geo{0}.tif".format(i))

str.format(*args, **kwargs)

Perform a string formatting operation. The string on which this method is called can contain literal text or replacement fields delimited by braces {}. Each replacement field contains either the numeric index of a positional argument, or the name of a keyword argument. Returns a copy of the string where each replacement field is replaced with the string value of the corresponding argument.

>>> "The sum of 1 + 2 is {0}".format(1+2)
'The sum of 1 + 2 is 3'

See Format String Syntax for a description of the various formatting options that can be specified in format strings.

This method of string formatting is the new standard in Python 3.0, and should be preferred to the % formatting described in String Formatting Operations in new code.

New in version 2.6.

You can use the operator % to inject strings into strings:

"first string is: %s, second one is: %s" % (str1, "geo.tif")

This will give:

"first string is: STR1CONTENTS, second one is geo.tif"

You could also do integers with %d:

"geo%d.tif" % 3   # geo3.tif