pandas pd.DataFrame.apply pandas.DataFrame.apply Basic Usage
Example
The pandas.DataFrame.apply() method is used to apply a given function to an entire DataFrame --- for example, computing the square root of every entry of a given DataFrame or summing across each row of a DataFrame to return a Series.
The below is a basic example of usage of this function:
# create a random DataFrame with 7 rows and 2 columns
df = pd.DataFrame(np.random.randint(0,100,size = (7,2)),
columns = ['fst','snd'])
>>> df
fst snd
0 40 94
1 58 93
2 95 95
3 88 40
4 25 27
5 62 64
6 18 92
# apply the square root function to each column:
# (this returns a DataFrame where each entry is the sqrt of the entry in df;
# setting axis=0 or axis=1 doesn't make a difference)
>>> df.apply(np.sqrt)
fst snd
0 6.324555 9.695360
1 7.615773 9.643651
2 9.746794 9.746794
3 9.380832 6.324555
4 5.000000 5.196152
5 7.874008 8.000000
6 4.242641 9.591663
# sum across the row (axis parameter now makes a difference):
>>> df.apply(np.sum, axis=1)
0 134
1 151
2 190
3 128
4 52
5 126
6 110
dtype: int64
>>> df.apply(np.sum)
fst 386
snd 505
dtype: int64
