The X object

The X object is a shortcut for writing simple, one-argument lambdas.

It’s roughly equivalent to this: lambda x: x

Example:

~X.some_attr.some_func(1, 2, 3).whatever
# produces:
lambda x: x.some_attr.some_func(1, 2, 3).whatever

~(X > 5)
# produces:
lambda x: x > 5

Any of the supported operations performed on an X object yield another one that remembers what was done to it, so they can be chained.

The ~ operator creates the actual function that can be called (without creating just another X instance). However, this can be omitted within pipe and pipe-utils context where X is converted to a function automatically:

users > where(X.is_staff) | foreach(X.first_name) | X[:10]

But you can make use of X even outside pipetools, you just have to remember to prefix it with ~

my_list = list(users)
my_list.sort(key=~X.last_login.date())

Currently supported operations

These are added as I need them. It’s quite complete now, but if you’re still missing something you can add it yourself or create an issue on github.

• call (__call__):

  X()
  X(some, agrs, some=kwargs)
  

• equals (__eq__):

  X == something
  

• not equal (__ne__):

  X != something
  

• attribute access (__getattr__):

  X.attr
  getattr(X, 'something')
  

• item access, slicing (__getitem__):

  X['key']
  X[0]
  X[:10]
  X[::-1]
  

• greater than (__gt__):

  X > 3
  

• greater or equal (__ge__):

  X >= 3
  

• less than (__lt__):

  X < 3
  

• less or equal (__le__):

  X <= 3
  

• modulo (__mod__):

  X % 2
  

• negate (__neg__):

  -X
  

• multiplication (__mul__):

  X * 3
  

• division (__div__):

  X / 3
  

• addition (__add__):

  X + 3
  X + " ...that's what she said!"
  

• subtraction (__sub__):

  X - 3
  

• power (__pow__):

  X ** 2
  

• is contained in (_in_)

  Unfortunately, X in container can’t be done (because the magic method is called on the container) so there’s a special method for that:

  X._in_(container)