Python: Replace "{}" in DataFrame

Question

I have dataframe (in a matrix form) where each cell is either 0 or {}. I want to replace the {} for 1.

I tried the following:

df.replace({},1)

and

for col in df:
    for i, val in enumerate(col):
        if df[col][i] == {}:
            df[col][i] = 1

Both are not working. There are no errors, just the {} does not get replace. Is there an issue with {} ? I got this matrix by applying pd.DataFrame(some dictionary).

enumerate is the wrong thing to do here, you should use iterrows or iteritems but the best thing to do is create the boolean mask and then just set the values — EdChum
– EdChum, Commented Apr 22, 2014 at 20:33

EdChum · Accepted Answer · 2014-04-22 21:19:53Z

3

Use boolean indexing to locate where you have matches and set the value:

In [2]:

import pandas as pd
df = pd.DataFrame({'a':[0,{},0], 'b':[{}, 0, 0]})
df

Out[2]:

    a   b
0   0  {}
1  {}   0
2   0   0

[3 rows x 2 columns]

In [19]:

for col in df:
    df[col][df[col]=={}]=1

df

Out[19]:

   a  b

0  0  1
1  1  0
2  0  0

[3 rows x 2 columns]

EDIT

Better is to do the mask on the entire dataframe, also you shouldn't perform chain indexing, thanks @Jeff for pointing out the error in my ways:

In [35]:

df[df=={}]=1

df

Out[35]:

   a  b
0  0  1
1  1  0
2  0  0

[3 rows x 2 columns]

edited Apr 22, 2014 at 21:19

answered Apr 22, 2014 at 20:26

EdChum

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1 Comment

EdChum Over a year ago

@Jeff I've updated my answer, I think I did try that initally and it gave me an error, I think it was a syntax error but I just tried it again and it worked so I've updated my answer

Luigi · Accepted Answer · 2014-04-22 20:23:09Z

0

Try this:

for col in df:
    for i in range(0,len(col)):
        if col[i] == {}:
            col[i] = 1

replace will not work as it is a built-in that operates on strings. The only problem with your second method is that you were using the values of each column instead of the indices.

answered Apr 22, 2014 at 20:23

Luigi

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