How to replace negative numbers in Pandas Data Frame by zero

Question

I would like to know if there is someway of replacing all DataFrame negative numbers by zeros

User · Answer

Another clean option that I have found useful is pandas.DataFrame.mask which will "replace values where the condition is true."

Create the DataFrame:

In [2]: import pandas as pd

In [3]: df = pd.DataFrame({'a': [0, -1, 2], 'b': [-3, 2, 1]})

In [4]: df
Out[4]: 
   a  b
0  0 -3
1 -1  2
2  2  1

Replace negative numbers with 0:

In [5]: df.mask(df < 0, 0)
Out[5]: 
   a  b
0  0  0
1  0  2
2  2  1

Or, replace negative numbers with NaN, which I frequently need:

In [7]: df.mask(df < 0)
Out[7]: 
     a    b
0  0.0  NaN
1  NaN  2.0
2  2.0  1.0

User · Answer

With lambda function df  column     df  column   apply lambda x   x if x  gt  0 else 0

User · Answer

If you are dealing with a large df  40m x 700 in my case  it works much faster and memory savvy through iteration on columns with something like   for col in df columns      df col  df col   lt  0    0

User · Answer

If all your columns are numeric  you can use boolean indexing   In  1   import pandas as pd  In  2   df   pd DataFrame   a    0  -1  2    b    -3  2  1     In  3   df Out 3       a  b 0  0 -3 1 -1  2 2  2  1  In  4   df df  lt  0    0  In  5   df Out 5       a  b 0  0  0 1  0  2 2  2  1     For the more general case  this answer shows the private method  get numeric data   In  1   import pandas as pd  In  2   df   pd DataFrame   a    0  -1  2    b    -3  2  1                               c     foo    goo    bar      In  3   df Out 3       a  b    c 0  0 -3  foo 1 -1  2  goo 2  2  1  bar  In  4   num   df  get numeric data    In  5   num num  lt  0    0  In  6   df Out 6       a  b    c 0  0  0  foo 1  0  2  goo 2  2  1  bar     With timedelta type  boolean indexing seems to work on separate columns  but not on the whole dataframe  So you can do   In  1   import pandas as pd  In  2   df   pd DataFrame   a   pd to timedelta  0  -1  2    d                                b   pd to timedelta  -3  2  1    d      In  3   df Out 3            a       b 0  0 days -3 days 1 -1 days  2 days 2  2 days  1 days  In  4   for k  v in df iteritems                v v  lt  0    0               In  5   df Out 5           a      b 0 0 days 0 days 1 0 days 2 days 2 2 days 1 days     Update  comparison with a pd Timedelta works on the whole DataFrame   In  1   import pandas as pd  In  2   df   pd DataFrame   a   pd to timedelta  0  -1  2    d                                b   pd to timedelta  -3  2  1    d      In  3   df df  lt  pd Timedelta 0     0  In  4   df Out 4           a      b 0 0 days 0 days 1 0 days 2 days 2 2 days 1 days

User · Answer

Perhaps you could use pandas where args  like so   data frame   data frame where data frame  lt  0  0

User · Answer

Another succinct way of doing this is pandas DataFrame clip   For example   import pandas as pd  In  20   df   pd DataFrame   a    -1  100  -2     In  21   df Out 21         a 0   -1 1  100 2   -2  In  22   df clip lower 0  Out 22         a 0    0 1  100 2    0   There s also df clip lower 0

[python] How to replace negative numbers in Pandas Data Frame by zero

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