pandas cheatsheet and common use cases

pandas-cheatsheet.md

pivot_table

In : 
df = pd.DataFrame({
    "A": ["foo", "foo", "foo", "foo", "foo", "bar", "bar", "bar", "bar"],
    "B": ["one", "one", "one", "two", "two", "one", "one", "two", "two"],
    "C": ["small", "large", "large", "small", "small", "large", "small", "small", "large"],
    "D": [1, 2, 2, 3, 3, 4, 5, 6, 7]
})
In : 
df

Out :
	A	B	C	D
0	foo	one	small	1
1	foo	one	large	2
2	foo	one	large	2
3	foo	two	small	3
4	foo	two	small	3
5	bar	one	large	4
6	bar	one	small	5
7	bar	two	small	6
8	bar	two	large	7

In : 
pd.pivot_table(df, index='A', columns='B', values='C', aggfunc='count', fill_value=0)

Out :
B	one	two
A		
bar	2	2
foo	3	2

In : 
# Computa lo mismo que el anterior, pero en porcentajes
pd.pivot_table(df, index='A', columns='B', values='C',
               aggfunc=lambda x: x.count() * 100 / df.shape[0], fill_value=0, margins=True)

Out :
B	one	two	All
A			
bar	22.222222	22.222222	44.444444
foo	33.333333	22.222222	55.555556
All	55.555556	44.444444	100.000000

In : 
pd.pivot_table(df, index='A', columns='B', values='D', aggfunc='sum', fill_value=0)

Out :
B	one	two
A		
bar	9	13
foo	5	6