Pandas getting a list of all non Nan values

Question

I want to get all non nan values in a dataframe like:

    foo   foo2   foo3  foo4
a   NY    WA     AZ    NaN
b   DC    NaN    NaN   NaN
c   MA    CA     NaN   NaN

output:

[NY, WA, AZ, DC, MA, CA]

Answer 1

I couldn't find an exact answer for this question, so when I combined several answers into one,
thought to share the answer:

df.stack().values

The trick is that stack() is removing nans while stacking the values, the rest is just standard way of getting dataframe values into list.