>>> print "x: "+x
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: cannot concatenate 'str' and 'int' objects
Python 2.6 introduces string interpolation like Ruby/Perl. (Older versions used printf-style format strings.)
print "x: {x}".format(x=1234) # New in 2.6
print "x: %d" % x # Old
In perl, "$x" pulls the value of $x from the variable namespace. In your Py2.6 example, the "{x}" format in the string has nothing to do with a variable named x; rather it references the keyword args supplied to format.
To simulate perl's
print "x: $x";
print "x: {x}".format(x=x) >>> "X: %(x)s" % {"x":10}
'X: 10'