pandas dropna specific column

df.dropna()     #drop all rows that have any NaN values
df.dropna(how='all')

# Returns a new DataFrame omitting rows with null values

df4.na.drop().show()
# +---+------+-----+
# |age|height| name|
# +---+------+-----+
# | 10|    80|Alice|
# +---+------+-----+