how convert a dataframe with null values to csv?

When i use to_csv in koalas for converting a Data-frame to CSV, the null values fill with \"\" , but i want null values be null. The code is:

df.to_csv(path='test', num_files=1) How can set koalas to don’t do this for null values?

when I canverto it to pandas and save the pandas dataframe evry thing is ok:

pdf =df.to_pandas()
pdf.to_csv('t.csv')

[MammadTavakoli]

the problem is with space. when a cell value is space after save the as csv file, the space fill with \"\".

d = {'col1': ['a b ', '2'], 'col2': [' ', '4']}
kdf = ks.DataFrame(data=d, columns=['col1', 'col2'])
kdf.to_csv('t')

---

the problem solved with this code: kdf.to_csv('t', emptyValue='')

[HyukjinKwon]

Can you try to_csv(..., nullValue=" ")?