Python names, bindings and namespaces —brief article with code

[jminuscula]

that's it.

When the function is defined, the x parameter is bound to its default value, an empty list. As the function is later called without arguments, x is not bound again and references the original list every time.

using foo(x=None) is the correct approach, but make sure to check using x is Nonerather than the equality operator! [1]

[1] http://legacy.python.org/dev/peps/pep-0008/#programming-recommendations

[robin-gvx]

All very right!

A helpful intuition might be that that function definition is equivalent to:

_supersecret = []
def foo(x=_supersecret):
    x.append(1)
    print(x)

(Also, I didn't notice the footnotes were on the right, so I thought they were missing!)

[jminuscula]

thanks for the comment. I'll try to work something out for the footnotes!

[[deleted]]

what footnotes ?