如何将数组字典转换为 'flattened' 数据框？

Question

假设我有一个数组字典，例如：

favourite_icecreams = {
    'Josh': ['vanilla', 'banana'],
    'Greg': ['chocolate'],
    'Sarah': ['mint', 'vanilla', 'mango']
}

我想将其转换为 pandas 数据框，列为“Flavour”和“Person”。它应该是这样的：

Flavour	Person
vanilla	Josh
banana	Josh
chocolate	Greg
mint	Sarah
vanilla	Sarah
mango	Sarah

最有效的方法是什么？

Answer 1

您可以使用（生成器）理解，然后将其提供给 pd.DataFrame:

import pandas as pd

favourite_icecreams = {
    'Josh': ['vanilla', 'banana'],
    'Greg': ['chocolate'],
    'Sarah': ['mint', 'vanilla', 'mango']
}

data = ((flavour, person)
            for person, flavours in favourite_icecreams.items()
            for flavour in flavours)
df = pd.DataFrame(data, columns=('Flavour', 'Person'))

print(df)
     # Flavour Person
# 0    vanilla   Josh
# 1     banana   Josh
# 2  chocolate   Greg
# 3       mint  Sarah
# 4    vanilla  Sarah
# 5      mango  Sarah

Answer 2

您可以完全在 pandas 中使用 DataFrame.from_dict and df.stack:

In [453]: df = pd.DataFrame.from_dict(favourite_icecreams, orient='index').stack().reset_index().drop('level_1', 1)

In [455]: df.columns = ['Person', 'Flavour']

In [456]: df
Out[456]: 
  Person    Flavour
0   Josh    vanilla
1   Josh     banana
2   Greg  chocolate
3  Sarah       mint
4  Sarah    vanilla
5  Sarah      mango

Answer 3

一个选项是将 person 和 flavor 提取到单独的列表中，在 person 列表上使用 numpy repeat，最后创建 DataFrame：

from itertools import chain
person, flavour = zip(*favourite_icecreams.items())
lengths = list(map(len, flavour))
person = np.array(person).repeat(lengths)
flavour = chain.from_iterable(flavour)
pd.DataFrame({'person':person, 'flavour':flavour})

  person    flavour
0   Josh    vanilla
1   Josh     banana
2   Greg  chocolate
3  Sarah       mint
4  Sarah    vanilla
5  Sarah      mango

Answer 4

另一个解决方案，使用.explode()：

df = pd.DataFrame(
    {
        "Person": favourite_icecreams.keys(),
        "Flavour": favourite_icecreams.values(),
    }
).explode("Flavour")


print(df)

打印：

   Person    Flavour
0    Josh    vanilla
0    Josh     banana
1    Greg  chocolate
2   Sarah       mint
2   Sarah    vanilla
2   Sarah      mango

如何将数组字典转换为 'flattened' 数据框？

How can I convert a dict of arrays into a 'flattened' dataframe?

python

dictionary

dataframe

pandas