Python lambda does not accept tuple argument

python lambda tuples

Dmitry · Jul 4, 2012 · Viewed 49.4k times · Source

I am running Eclipse SDK v3.6 with PyDev v2.6 plugin on two PC, with Linux and Windows.

I would like to pass a tuple as an argument, like (just example):

foo = lambda (x,y): (y,x)
print (foo((1,2)))

This works on Linux and gives the result:

(2,1)

On Windows it rises an error:

foo = lambda (x,y): (y,x)
             ^
SyntaxError: invalid syntax

How to solve the problem?

Answer

You are probably running Python 3.x on Windows, and Python 2.x on Linux. The ability to unpack tuple parameters was removed in Python 3: See PEP 3113.

You can manually unpack the tuple instead, which would work on both Python 2.x and 3.x:

foo = lambda xy: (xy[1],xy[0])

Or:

def foo(xy):
    x,y = xy
    return (y,x)

Python lambda does not accept tuple argument

Answer

Related questions