DOC: update usage of randn in io.rst

[jorisvandenbossche]

In the IO page of the docs (https://github.com/pandas-dev/pandas/blob/master/doc/source/io.rst), there are some occurrences of direct calls to randn instead of using the properly imported np.random.randn in full, which makes the examples not reproducible if you only imported import numpy as np.

A PR that replaces randn with np.random.randn would thus be very welcome.

[charlesdong1991]

might because randn has been assigned to np.random.randn at very beginning in the import part? randn = np.random.randn

[jorisvandenbossche]

randn has been assigned to np.random.randn at very beginning in the import part?

Yes, that is the reason it currently works in our docs. But, that import is hidden to the viewer of the docs, and is not a standard numpy import. So therefore we want to fix this, with the goal to be able to remove this randn = np.random.randn

[charlesdong1991]

ok, i see... i will make a small pr on it...