akva wrote:
Hi All, what's the exact semantics of the |= operator in python? It seems that a |= d is not always equivalent to a = a | d
The manual explicitly specifies that mutable objects may implement the operation part of operation-assignments by updating in place -- so that the object assigned is a mutated version of the original rather than a new object.
The value equivalency only applies in the namespace in which the statement appears.
For example let's consider the following code: def foo(s): s = s | set([10]) def bar(s): s |= set([10]) s = set([1,2]) foo(s) print s # prints set([1, 2])
Put the print inside foo and you will get set([1,2,10]), as with bar.
bar(s) print s # prints set([1, 2, 10]) So it appears that inside bar function the |= operator modifies the value of s in place rather than creates a new value.
This has nothing to do with being inside a function. tjr -- http://mail.python.org/mailman/listinfo/python-list
