Assign Index¶

In [1]:

import pandas as pd

df = pd.DataFrame(
    {"x": [1, 2, 3, 4, 5], "y": [5, 4, 3, 2, 1]}, index=["r1", "r2", "r3", "r4", "r5"]
)

df.head()

Out[1]:

In [2]:

df.index = df.y
df

Out[2]:

set_index¶

In [21]:

import pandas as pd

df = pd.DataFrame(
    {"month": [1, 4, 7, 10], "year": [2012, 2014, 2013, 2014], "sale": [55, 40, 84, 31]}
)
df

Out[21]:

In [22]:

df2 = df.set_index("month")
df2

Out[22]:

In [23]:

df2.columns

Out[23]:

Index(['year', 'sale'], dtype='object')

In [7]:

df.year.iat[0]

Out[7]:

In [8]:

df.year.at[0]

Out[8]:

In [9]:

df2.year.iat[0]

Out[9]:

In [10]:

df2.year.at[1]

Out[10]:

In [24]:

df3 = df.set_index(["year", "month"])
df3

Out[24]:

In [16]:

import numpy as np

In [17]:

np.average([20000, 30000], weights=[9, 15])

Out[17]:

26250.0

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