对pandas中to_dict的用法详解

简介：pandas 中的to_dict 可以对dataframe类型的数据进行转换

可以选择六种的转换类型，分别对应于参数 ‘dict', ‘list', ‘series', ‘split', ‘records', ‘index'，下面逐一介绍每种的用法

help on method to_dict in module pandas.core.frame:
to_dict(orient='dict') method of pandas.core.frame.dataframe instance
 convert dataframe to dictionary.
 parameters
 ----------
 orient : str {'dict', 'list', 'series', 'split', 'records', 'index'}
 determines the type of the values of the dictionary.
 - dict (default) : dict like {column -> {index -> value}}
 - list : dict like {column -> [values]}
 - series : dict like {column -> series(values)}
 - split : dict like
  {index -> [index], columns -> [columns], data -> [values]}
 - records : list like
  [{column -> value}, ... , {column -> value}]
 - index : dict like {index -> {column -> value}}
  .. versionadded:: 0.17.0
 abbreviations are allowed. `s` indicates `series` and `sp`
 indicates `split`.
 returns
 -------
 result : dict like {column -> {index -> value}}

1、选择参数orient='dict'

dict也是默认的参数，下面的data数据类型为dataframe结构, 会形成 {column -> {index -> value}}这样的结构的字典，可以看成是一种双重字典结构

- 单独提取每列的值及其索引，然后组合成一个字典

- 再将上述的列属性作为关键字（key），值（values）为上述的字典

查询方式为 ：data_dict[key1][key2]

- data_dict 为参数选择orient='dict'时的数据名

- key1 为列属性的键值（外层）

- key2 为内层字典对应的键值

data 
out[9]: 
 pclass age embarked   home.dest sex
1086 3rd 31.194181 unknown   unknown male
12 1st 31.194181 cherbourg   paris, france female
1036 3rd 31.194181 unknown   unknown male
833 3rd 32.000000 southampton foresvik, norway portland, nd male
1108 3rd 31.194181 unknown   unknown male
562 2nd 41.000000 cherbourg   new york, ny male
437 2nd 48.000000 southampton somerset / bernardsville, nj female
663 3rd 26.000000 southampton   unknown male
669 3rd 19.000000 southampton   england male
507 2nd 31.194181 southampton  petworth, sussex male
in[10]: data_dict=data.to_dict(orient= 'dict')
in[11]: data_dict
out[11]: 
{'age': {12: 31.19418104265403,
 437: 48.0,
 507: 31.19418104265403,
 562: 41.0,
 663: 26.0,
 669: 19.0,
 833: 32.0,
 1036: 31.19418104265403,
 1086: 31.19418104265403,
 1108: 31.19418104265403},
 'embarked': {12: 'cherbourg',
 437: 'southampton',
 507: 'southampton',
 562: 'cherbourg',
 663: 'southampton',
 669: 'southampton',
 833: 'southampton',
 1036: 'unknown',
 1086: 'unknown',
 1108: 'unknown'},
 'home.dest': {12: 'paris, france',
 437: 'somerset / bernardsville, nj',
 507: 'petworth, sussex',
 562: 'new york, ny',
 663: 'unknown',
 669: 'england',
 833: 'foresvik, norway portland, nd',
 1036: 'unknown',
 1086: 'unknown',
 1108: 'unknown'},
 'pclass': {12: '1st',
 437: '2nd',
 507: '2nd',
 562: '2nd',
 663: '3rd',
 669: '3rd',
 833: '3rd',
 1036: '3rd',
 1086: '3rd',
 1108: '3rd'},
 'sex': {12: 'female',
 437: 'female',
 507: 'male',
 562: 'male',
 663: 'male',
 669: 'male',
 833: 'male',
 1036: 'male',
 1086: 'male',
 1108: 'male'}}

2、当关键字orient=' list' 时

和1中比较相似，只不过内层变成了一个列表，结构为{column -> [values]}

查询方式为： data_list[keys][index]

data_list 为关键字orient='list' 时对应的数据名

keys 为列属性的键值，如本例中的'age' , ‘embarked'等

index 为整型索引，从0开始到最后

in[19]: data_list=data.to_dict(orient='list')
in[20]: data_list
out[20]: 
{'age': [31.19418104265403,
 31.19418104265403,
 31.19418104265403,
 32.0,
 31.19418104265403,
 41.0,
 48.0,
 26.0,
 19.0,
 31.19418104265403],
 'embarked': ['unknown',
 'cherbourg',
 'unknown',
 'southampton',
 'unknown',
 'cherbourg',
 'southampton',
 'southampton',
 'southampton',
 'southampton'],
 'home.dest': ['unknown',
 'paris, france',
 'unknown',
 'foresvik, norway portland, nd',
 'unknown',
 'new york, ny',
 'somerset / bernardsville, nj',
 'unknown',
 'england',
 'petworth, sussex'],
 'pclass': ['3rd',
 '1st',
 '3rd',
 '3rd',
 '3rd',
 '2nd',
 '2nd',
 '3rd',
 '3rd',
 '2nd'],
 'sex': ['male',
 'female',
 'male',
 'male',
 'male',
 'male',
 'female',
 'male',
 'male',
 'male']}

3、关键字参数orient='series'

形成结构{column -> series(values)}

调用格式为：data_series[key1][key2]或data_dict[key1]

data_series 为数据对应的名字

key1 为列属性的键值，如本例中的'age' , ‘embarked'等

key2 使用数据原始的索引（可选）

in[21]: data_series=data.to_dict(orient='series')
in[22]: data_series
out[22]: 
{'age': 1086 31.194181
 12 31.194181
 1036 31.194181
 833 32.000000
 1108 31.194181
 562 41.000000
 437 48.000000
 663 26.000000
 669 19.000000
 507 31.194181
 name: age, dtype: float64, 'embarked': 1086 unknown
 12 cherbourg
 1036 unknown
 833 southampton
 1108 unknown
 562 cherbourg
 437 southampton
 663 southampton
 669 southampton
 507 southampton
 name: embarked, dtype: object, 'home.dest': 1086    unknown
 12   paris, france
 1036    unknown
 833 foresvik, norway portland, nd
 1108    unknown
 562   new york, ny
 437 somerset / bernardsville, nj
 663    unknown
 669    england
 507   petworth, sussex
 name: home.dest, dtype: object, 'pclass': 1086 3rd
 12 1st
 1036 3rd
 833 3rd
 1108 3rd
 562 2nd
 437 2nd
 663 3rd
 669 3rd
 507 2nd
 name: pclass, dtype: object, 'sex': 1086 male
 12 female
 1036 male
 833 male
 1108 male
 562 male
 437 female
 663 male
 669 male
 507 male
 name: sex, dtype: object}

4、关键字参数orient='split'

形成{index -> [index], columns -> [columns], data -> [values]}的结构，是将数据、索引、属性名单独脱离出来构成字典

调用方式有 data_split[‘index'],data_split[‘data'],data_split[‘columns']

data_split=data.to_dict(orient='split')
data_split
out[38]: 
{'columns': ['pclass', 'age', 'embarked', 'home.dest', 'sex'],
 'data': [['3rd', 31.19418104265403, 'unknown', 'unknown', 'male'],
 ['1st', 31.19418104265403, 'cherbourg', 'paris, france', 'female'],
 ['3rd', 31.19418104265403, 'unknown', 'unknown', 'male'],
 ['3rd', 32.0, 'southampton', 'foresvik, norway portland, nd', 'male'],
 ['3rd', 31.19418104265403, 'unknown', 'unknown', 'male'],
 ['2nd', 41.0, 'cherbourg', 'new york, ny', 'male'],
 ['2nd', 48.0, 'southampton', 'somerset / bernardsville, nj', 'female'],
 ['3rd', 26.0, 'southampton', 'unknown', 'male'],
 ['3rd', 19.0, 'southampton', 'england', 'male'],
 ['2nd', 31.19418104265403, 'southampton', 'petworth, sussex', 'male']],
 'index': [1086, 12, 1036, 833, 1108, 562, 437, 663, 669, 507]}

5、当关键字orient='records' 时

形成[{column -> value}, … , {column -> value}]的结构

整体构成一个列表，内层是将原始数据的每行提取出来形成字典

调用格式为data_records[index][key1]

data_records=data.to_dict(orient='records')
data_records
out[41]: 
[{'age': 31.19418104265403,
 'embarked': 'unknown',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 {'age': 31.19418104265403,
 'embarked': 'cherbourg',
 'home.dest': 'paris, france',
 'pclass': '1st',
 'sex': 'female'},
 {'age': 31.19418104265403,
 'embarked': 'unknown',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 {'age': 32.0,
 'embarked': 'southampton',
 'home.dest': 'foresvik, norway portland, nd',
 'pclass': '3rd',
 'sex': 'male'},
 {'age': 31.19418104265403,
 'embarked': 'unknown',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 {'age': 41.0,
 'embarked': 'cherbourg',
 'home.dest': 'new york, ny',
 'pclass': '2nd',
 'sex': 'male'},
 {'age': 48.0,
 'embarked': 'southampton',
 'home.dest': 'somerset / bernardsville, nj',
 'pclass': '2nd',
 'sex': 'female'},
 {'age': 26.0,
 'embarked': 'southampton',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 {'age': 19.0,
 'embarked': 'southampton',
 'home.dest': 'england',
 'pclass': '3rd',
 'sex': 'male'},
 {'age': 31.19418104265403,
 'embarked': 'southampton',
 'home.dest': 'petworth, sussex',
 'pclass': '2nd',
 'sex': 'male'}]

6、当关键字orient='index' 时

形成{index -> {column -> value}}的结构，调用格式正好和'dict' 对应的反过来，请读者自己思考

data_index=data.to_dict(orient='index')
data_index
out[43]: 
{12: {'age': 31.19418104265403,
 'embarked': 'cherbourg',
 'home.dest': 'paris, france',
 'pclass': '1st',
 'sex': 'female'},
 437: {'age': 48.0,
 'embarked': 'southampton',
 'home.dest': 'somerset / bernardsville, nj',
 'pclass': '2nd',
 'sex': 'female'},
 507: {'age': 31.19418104265403,
 'embarked': 'southampton',
 'home.dest': 'petworth, sussex',
 'pclass': '2nd',
 'sex': 'male'},
 562: {'age': 41.0,
 'embarked': 'cherbourg',
 'home.dest': 'new york, ny',
 'pclass': '2nd',
 'sex': 'male'},
 663: {'age': 26.0,
 'embarked': 'southampton',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 669: {'age': 19.0,
 'embarked': 'southampton',
 'home.dest': 'england',
 'pclass': '3rd',
 'sex': 'male'},
 833: {'age': 32.0,
 'embarked': 'southampton',
 'home.dest': 'foresvik, norway portland, nd',
 'pclass': '3rd',
 'sex': 'male'},
 1036: {'age': 31.19418104265403,
 'embarked': 'unknown',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 1086: {'age': 31.19418104265403,
 'embarked': 'unknown',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'},
 1108: {'age': 31.19418104265403,
 'embarked': 'unknown',
 'home.dest': 'unknown',
 'pclass': '3rd',
 'sex': 'male'}}

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