Pandas dataframe replace value on condition

Question

I have the following dataframe:

    limit1  limit2 
a    123     567
b    65      0
c    123     1233
d    0987    0
e    231451  0998

I want to create a new frame with the lower limit for each row. Except when there is a 0, in which case the value from the other column is taken.

desired output:

    limit1  limit2
a    123     567
b    65      65
c    123     1233
d    0987    0987
e    231451  0998

As you can see the 0 on the right are replaced with the value from the corresponding row from the left.

My following code does not work:

low_limit = pd.concat([limit1, limit2], join='outer', axis=1)
if limit2 == 0:
    low_limit = limit1
else:
    low_limit.min(axis=1).dropna()

the error:

ValueError: The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().

Please provide a [mcve], as well as the entire error output. What do you understand from that error message? — AMC, Oct 21 '20 at 01:33
Does this answer your question? [Truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all()](https://stackoverflow.com/questions/36921951/truth-value-of-a-series-is-ambiguous-use-a-empty-a-bool-a-item-a-any-o) — AMC, Oct 21 '20 at 01:33

score 1 · Accepted Answer · answered Oct 21 '20 at 00:56

1

Use np.where(condition, outcome if condition is True, outcome ifcondition false)

df['limit2']=np.where(df.limit2==0,df.limit1,df.min(1))

    limit1  limit2
a     123     123
b      65      65
c     123     123
d     987     987
e  231451     998

answered Oct 21 '20 at 00:56

wwnde

26,119
6
18
32

score 0 · Answer 2 · answered Oct 21 '20 at 00:55

So you can do replace since min(NaN, not NaN value) out put the not null value

df.limit2 = df.replace({'limit2' : {0 : np.nan}}).min(axis=1)
df
Out[46]: 
   limit1  limit2
a     123   123.0
b      65    65.0
c     123   123.0
d     987   987.0
e  231451   998.0

Pandas dataframe replace value on condition

2 Answers2