GitLab

(part of the long-term plan of supporting Python 2 and 3 in the same code base
without 2to3)

to precision)

numpy.

This should be *lower* than that of Unit (and ScaledUnit/BaseUnit), since we
still want Units to take priority over Quantities (but Quantity to take
precedence over regular ndarrays) for reasons like this:

>>> a = np.array([1]) * u.angstroms
>>> b = a * u.angstroms # should be np.array([1])*u.angstroms**2
>>> np.arange(10) * a # utilize broadcasting
[1 2 3 4 5 6 7 8 9 10] A**2

The main thing that's done here is that numpy arrays can be given units via the
* operator, rather than relying on the Quantity constructor

e.g.,

>>> import numpy as np
>>> np.zeros(10) * u.angstroms
Quantity(value=array([ 0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.,  0.]), unit=angstrom)

yay!

- Add an informative __repr__ to Topology
- Add __len__ to Chain and Residue to quickly tell how many residues or atoms
  are in them, respectively