Extract first and last row of a dataframe in pandas
I think you can try add parameter axis=1
to concat
, because output of df.iloc[0,:]
and df.iloc[-1,:]
are Series
and transpose by T
:
print df.iloc[0,:]
a 1
b a
Name: 0, dtype: object
print df.iloc[-1,:]
a 4
b d
Name: 3, dtype: object
print pd.concat([df.iloc[0,:], df.iloc[-1,:]], axis=1)
0 3
a 1 4
b a d
print pd.concat([df.iloc[0,:], df.iloc[-1,:]], axis=1).T
a b
0 1 a
3 4 d
You can also use head
and tail
:
In [29]: pd.concat([df.head(1), df.tail(1)])
Out[29]:
a b
0 1 a
3 4 d
The accepted answer duplicates the first row if the frame only contains a single row. If that's a concern
df[0::len(df)-1 if len(df) > 1 else 1]
works even for single row-dataframes.
Example: For the following dataframe this will not create a duplicate:
df = pd.DataFrame({'a': [1], 'b':['a']})
df2 = df[0::len(df)-1 if len(df) > 1 else 1]
print df2
a b
0 1 a
whereas this does:
df3 = df.iloc[[0, -1]]
print df3
a b
0 1 a
0 1 a
because the single row is the first AND last row at the same time.
I think the most simple way is .iloc[[0, -1]]
.
df = pd.DataFrame({'a':range(1,5), 'b':['a','b','c','d']})
df2 = df.iloc[[0, -1]]
print(df2)
a b
0 1 a
3 4 d