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Python pandas Filtering out nan from a data selection of a column of strings

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How do you filter out NaN values pandas?

You can filter out rows with NAN value from pandas DataFrame column string, float, datetime e.t.c by using DataFrame. dropna() and DataFrame. notnull() methods. Python doesn't support Null hence any missing data is represented as None or NaN.

How do you filter a DataFrame based on column values?

Using query() to Filter by Column Value in pandas DataFrame. query() function is used to filter rows based on column value in pandas. After applying the expression, it returns a new DataFrame. If you wanted to update the existing DataFrame use inplace=True param.


Just drop them:

nms.dropna(thresh=2)

this will drop all rows where there are at least two non-NaN.

Then you could then drop where name is NaN:

In [87]:

nms
Out[87]:
  movie    name  rating
0   thg    John       3
1   thg     NaN       4
3   mol  Graham     NaN
4   lob     NaN     NaN
5   lob     NaN     NaN

[5 rows x 3 columns]
In [89]:

nms = nms.dropna(thresh=2)
In [90]:

nms[nms.name.notnull()]
Out[90]:
  movie    name  rating
0   thg    John       3
3   mol  Graham     NaN

[2 rows x 3 columns]

EDIT

Actually looking at what you originally want you can do just this without the dropna call:

nms[nms.name.notnull()]

UPDATE

Looking at this question 3 years later, there is a mistake, firstly thresh arg looks for at least n non-NaN values so in fact the output should be:

In [4]:
nms.dropna(thresh=2)

Out[4]:
  movie    name  rating
0   thg    John     3.0
1   thg     NaN     4.0
3   mol  Graham     NaN

It's possible that I was either mistaken 3 years ago or that the version of pandas I was running had a bug, both scenarios are entirely possible.


Simplest of all solutions:

filtered_df = df[df['name'].notnull()]

Thus, it filters out only rows that doesn't have NaN values in 'name' column.

For multiple columns:

filtered_df = df[df[['name', 'country', 'region']].notnull().all(1)]

df.dropna(subset=['columnName1', 'columnName2'])

df = pd.DataFrame({'movie': ['thg', 'thg', 'mol', 'mol', 'lob', 'lob'],'rating': [3., 4., 5., np.nan, np.nan, np.nan],'name': ['John','James', np.nan, np.nan, np.nan,np.nan]})

for col in df.columns:
    df = df[~pd.isnull(df[col])]