Python pandas: output dataframe to csv with integers

The answer I was looking for was a slight variation of what @Jeff proposed in his answer. The credit goes to him. This is what solved my problem in the end for reference:

import pandas
df = pandas.DataFrame(data, columns=['a','b','c','d'], index=['x','y','z'])
df = df.fillna(0)
df = df.astype(int)
df.to_csv('test.csv', sep='\t')