ǹp.array is written in C, and is part of the multiarray module that is defined here:

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/multiarraymodule.c

The "array" name is mapped here:

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/multiarraymodule.c#L4093

to the function _array_fromobject defined here:

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/multiarraymodule.c#L1557

That functions does some checking and has a couple of fast paths for the case where the input is already an array or a subclass, but for the general case it relies on PyArray_CheckFromAny:

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/ctors.c#L1848

which in turn calls Pyarray_FromAny:

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/ctors.c#L1674

You will also haveto take a look at what goes on in PyArray_GetArrayParamsFromObject, which gets called by PyArray_FromAny;

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/ctors.c#L1428

as well as several other places, but I think they are all (or most of them) in ctors.c.

You may also want to take a llok at PyArray_FromIter, which is the function that ultimately takes care of calls to np.fromiter:

https://github.com/numpy/numpy/blob/maintenance/1.11.x/numpy/core/src/multiarray/ctors.c#L3657

Written by Jaime Fernández del Río as an answer to query on the mailing list