I want to update the first row of a dataframe that meets a certain condition. Like in this question Get first row of dataframe in Python Pandas based on criteria but for setting instead of just selecting.
df[df['Qty'] > 0].iloc[0] = 5
The above line does not seem to do anything.
Given df below:
a b
0 1 2
1 2 1
2 3 1
you change the values in the first row where the value in column b is equal to 1 by:
df.loc[df[df['b'] == 1].index[0]] = 1000
Output:
a b
0 1 2
1 1000 1000
2 3 1
If you want to change the value in a specific column(s), you can do that too:
df.loc[df[df['b'] == 1].index[0],'a'] = 1000
a b
0 1 2
1 1000 1
2 3 1
I believe what you're looking for is:
idx = df[df['Qty'] > 0].index[0]
df.loc[[idx], ['Qty']] = 5