Insert Row in Python Pandas DataFrame

Question

(I´m new to python, sorry for any mistakes I make, I hope you can understand me)

I have searched for a method to insert a Row into a Pandas DataFrame in Python, and I have found this:

add one row in a pandas.DataFrame

I have use the code provided in the accepted answer of that topic by fred, but the code overwrites my row: My code (Inserts a row with values "-1" for each column in certains conditions):

df.loc[i+1] = [-1 for n in range(len(df.columns))]

How can I make the code insert a row WITHOUT overriding it? For example, if I have a 50 row DataFrame, insert a row in position 25 (Just as an example), and make the DataFrame have 51 rows (Being the 25 a extra NEW row).

I hope you can understand my question. (Sorry for any english mistakes)

Thank you.

UPDATE:

Someone suggested this:

Is it possible to insert a row at an arbitrary position in a dataframe using pandas?

Tried, did not work. In fact, it does nothing, does not add any row.

 line = pd.DataFrame({[-1 for n in range(len(df.columns))]}, index=[i+1])
 df = pd.concat([ df.ix[:i],  line,  df.ix[i+1:]]).reset_index(drop=True)

Any other ideas?

Answer 1

With a small DataFrame, if you want to insert a line, at position 1:

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

df1 = pd.DataFrame([4,5]).T  

pd.concat([df[:1], df1.rename(columns=dict(zip(df1.columns,df.columns))), df[1:]])

#Out[46]: 
#   a  b
#0  0  2
#0  4  5
#1  1  3