How to insert row to dataframe

Question

I have an existing dataframe like this

>>> print(dataframe)
sid
30      11
56       5
73      25
78       2
132      1
        ..
8531    25
8616     2
9049     1
9125     6
9316    11
Name: name, Length: 87, dtype: int64

I want to add a row like {'sid': 2, '': 100} to it but when I try this

df = pandas.DataFrame({'sid': [2], '': [100]})
df = df.set_index('sid')
dataframe = dataframe.append(df)
print(dataframe)

I end up with

sid              
30    11.0    NaN
56     5.0    NaN
73    25.0    NaN
78     2.0    NaN
132    1.0    NaN
...    ...    ...
8616   2.0    NaN
9049   1.0    NaN
9125   6.0    NaN
9316  11.0    NaN
2      NaN  100.0

I'm hoping for something more like

sid
2       100
30      11
56       5
73      25
78       2
132      1
        ..
8531    25
8616     2
9049     1
9125     6
9316    11

Any idea how I can achieve that?

Answer 1

Reason for the above problem, because at the time you have appended two DataFrames, you forgot to set 'sid' as the dataframe index. So, basically the two DataFrames has different structure when you append it. Make sure to set the index of both dataframes same before you append them.

data = [ [30,11], [56, 5], [73, 25]]    #test dataframe 
dataframe = pd.DataFrame(data, columns=['sid', ''])
dataframe = dataframe.set_index('sid')
print(dataframe)

You get,

sid    
30   11
56    5
73   25

Create and set the index of df,

df = pd.DataFrame({'sid' : [2], '' : [100]})
df = df.set_index('sid')

You get,

sid     
2    100

Then append them,

dataframe = df.append(dataframe)
print(dataframe)

You will get the disired outcome,

sid     
2    100
30    11
56     5
73    25

Answer 2

The way to do this was

dataframe.loc[2] = 100

Thanks anky!