Replace an empty string in a list with NaN

Question

I am trying to replace an empty string in a list with a known string (say 'NAN'). I am using the following command

a = ['','','asdf']    
["nan" if x =='' else x for x in a]

The code is working, when it is used standalone, however when I am trying to employ it in my main code, it is not working. My main code is as follows:

data = [ ('plant_data.xlsx', 0, []),('sorg.xlsx', 1, ['','','asdf'])]#,('sloc.xlsx', 1, ['307-040N'])];


for fl in data:
    filename = fl[0];
    filename = filename[:-5];

    f = open('IC1_Results\%s.txt' %filename,'w');

    if fl[1] == 0:
        f.write("All Part Numbers exist");
        f.close()

    elif fl[1] == 1:
        a = fl[2];
        print type(a)

        ["nan" if x == '' else x for x in a]

        print fl[2],a

a = ["nan" if x == '' else x for x in a] ?

Rakesh
– Rakesh

2018-06-26 14:51:06 +00:00
Commented Jun 26, 2018 at 14:51 — Rakesh
– Rakesh, Commented Jun 26, 2018 at 14:51

Mathieu · Accepted Answer · 2018-06-26 14:51:30Z

5

It is working but you are simply running it without assigning the output to any location. Change the line with:

fl[2] = ["nan" if x == '' else x for x in a]

Or maybe:

a = ["nan" if x == '' else x for x in a]

Depending on where you want to store it...

answered Jun 26, 2018 at 14:51

Mathieu

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Comments

Taohidul Islam · Accepted Answer · 2018-06-26 14:52:15Z

2

You're creating this ["nan" if x == '' else x for x in a] list, but you're not assigning it! Your code should be like a= ["nan" if x == '' else x for x in a].

answered Jun 26, 2018 at 14:52

Taohidul Islam

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Lix · Accepted Answer · 2018-06-26 14:52:10Z

1

The output of list comprehension is a new list - what you'll need to do is override your existing list (or create a new one to hold the results)

a = ["nan" if x == '' else x for x in a]

I believe that the reason you though it was working in a standalone script is that when you execute the list comprehension as-is, python will print the list to the screen, but if you want to use this new list, you'll need to save it to a variable.

answered Jun 26, 2018 at 14:52

Lix

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Comments

StardustGogeta · Accepted Answer · 2019-07-30 16:24:39Z

0

Here's another option that uses the isinstance() method. Using basestring works for both plain strings and Unicode strings.

[np.nan if isinstance(x, basestring) else x for x in a]

edited Jul 30, 2019 at 16:24

StardustGogeta

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answered Jul 30, 2019 at 15:10

Nunya

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