How can I remove Nan from list Python NumPy

Question

I have a list that countain values  one of the values I got is  nan   countries   nan   USA    UK    France     I tried to remove it  but I everytime get an error   cleanedList    x for x in countries if  math isnan x     True   TypeError  a float is required   When I tried this one     cleanedList   cities np logical not np isnan countries    cleanedList   cities  np isnan countries    TypeError  ufunc  isnan  not supported for the input types  and the inputs could not be safely coerced to any supported types according to the casting rule   safe

User · Answer

In your example  nan  is a string so instead of using isnan   just check for the string  like this   cleanedList    x for x in countries if x     nan

User · Answer

if you check for the element type  type countries 1     the result will be  lt class float gt  so you can use the following code    i for i in countries if type i  is not float

User · Answer

I like to remove missing values from a list like this   list no nan    x for x in list with nan if pd notnull x

User · Answer

Using your example where     countries   nan   USA    UK    France    Since nan is not equal to nan  nan    nan  and countries 0    nan  you should observe the following   countries 0     countries 0  False   However    countries 1     countries 1  True countries 2     countries 2  True countries 3     countries 3  True   Therefore  the following should work   cleanedList    x for x in countries if x    x

User · Answer

I noticed that Pandas for example will return  nan  for blank values  Since it s not a string you need to convert it to one in order to match it  For example   ulist   df column1 unique    create a list from a column with Pandas which  for loc in ulist      loc   str loc     here  nan  is converted to a string to compare with if     if loc     nan           print loc

User · Answer

Another way to do it would include using filter like this   countries   list filter lambda x  str x      nan   countries

User · Answer

The question has changed  so to has the answer  Strings can t be tested using math isnan as this expects a float argument  In your countries list  you have floats and strings  In your case the following should suffice  cleanedList    x for x in countries if str x      nan     Old answer In your countries list  the literal  nan  is a string not the Python float nan which is equivalent to  float  NaN    In your case the following should suffice  cleanedList    x for x in countries if x     nan

User · Answer

The problem comes from the fact that np isnan   does not handle string values correctly  For example  if you do   np isnan  A   TypeError  ufunc  isnan  not supported for the input types  and the inputs could not be safely coerced to any supported types according to the casting rule   safe     However the pandas version pd isnull   works for numeric and string values   pd isnull  A    gt  False  pd isnull 3   gt  False  pd isnull np nan   gt  True  pd isnull None   gt  True

User · Answer

use numpy fancy indexing   In  29   countries np asarray countries   In  30   countries countries   nan   Out 30    array   USA    UK    France           dtype   S6

User · Answer

import numpy as np  mylist    3  4  5  np nan  l    x for x in mylist if  np isnan x     This should remove all NaN  Of course  I assume that it is not a string here but actual NaN  np nan

[python] How can I remove Nan from list Python/NumPy

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