Replacing blank values (white space) with NaN in pandas

Michael Zippo

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I want to find all values in a Pandas dataframe that contain whitespace (any arbitrary amount) and replace those values with NaNs.

Any ideas how this can be improved?

Basically I want to turn this:

                   A    B    C
2000-01-01 -0.532681  foo    0
2000-01-02  1.490752  bar    1
2000-01-03 -1.387326  foo    2
2000-01-04  0.814772  baz     
2000-01-05 -0.222552         4
2000-01-06 -1.176781  qux

Into this:

                   A     B     C
2000-01-01 -0.532681   foo     0
2000-01-02  1.490752   bar     1
2000-01-03 -1.387326   foo     2
2000-01-04  0.814772   baz   NaN
2000-01-05 -0.222552   NaN     4
2000-01-06 -1.176781   qux   NaN

I"ve managed to do it with the code below, but man is it ugly. It"s not Pythonic and I"m sure it"s not the most efficient use of pandas either. I loop through each column and do boolean replacement against a column mask generated by applying a function that does a regex search of each value, matching on whitespace.

for i in df.columns:
    df[i][df[i].apply(lambda i: True if re.search("^s*$", str(i)) else False)]=None

It could be optimized a bit by only iterating through fields that could contain empty strings:

if df[i].dtype == np.dtype("object")

But that"s not much of an improvement

And finally, this code sets the target strings to None, which works with Pandas" functions like fillna(), but it would be nice for completeness if I could actually insert a NaN directly instead of None.

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Manuel Krasiko

Tallinn | 2023-01-27

Thanks for explaining! I was stuck with Replacing blank values (white space) with NaN in pandas for some hours, finally got it done 🤗. Will use it in my bachelor thesis

Frank Galleotti

London | 2023-01-27

Maybe there are another answers? What Replacing blank values (white space) with NaN in pandas exactly means?. Will use it in my bachelor thesis

Schneider Innsbruck

Abu Dhabi | 2023-01-27

Maybe there are another answers? What Replacing blank values (white space) with NaN in pandas exactly means?. Will get back tomorrow with feedback