如何从 DataFrame 熊猫对象中选择特定列？答案

【问题标题】：How to select specific columns from a DataFrame pandas object?如何从 DataFrame 熊猫对象中选择特定列？
【发布时间】：2016-08-18 04:11:41
【问题描述】：

我使用Quandl python 模块中的get() 函数从Quandl 下载了一个时间序列，并调用了UNES_HARD_COAL_BR，它的形状为(24,19)，但我只想使用第1 到第3 列和第 18 列。我编写了这个脚本来使用名为ll 的列表完成这项工作，并在我的DataFrame 对象中应用drop() 方法，该列表包含我不使用的列的名称。 这里的挑战是在不创建列表的情况下做到这一点。

import Quandl
import pandas as pd

UNES_HARD_COAL_BR = Quandl.get("UENG/CL_BRA", authtoken="xX6ntNSFuvq7eCZvDdvL")
UNES_HARD_COAL_BR.columns = UNES_HARD_COAL_BR.columns.str.replace(' ', '_')



ll =['Hard_coal_-_transformation_(Metric_tons,_thousand)', 'Hard_coal_-_transformation_in_coke_ovens_(Metric_tons,_thousand)','Hard_coal_-_transformation_in_electricity,_CHP_and_heat_plants_(Metric_tons,_thousand)','Hard_coal_-_transformation_in_electricity_plants_-_main_activity_producers_(Metric_tons,_thousand)','Hard_coal_-_final_energy_consumption_(Metric_tons,_thousand)','Hard_coal_-_consumption_by_manufacturing,_construction_and_non-fuel_mining_industry_(Metric_tons,_thousand)','Hard_coal_-_consumption_by_other_manuf.,_const._and_non-fuel_ind._(Metric_tons,_thousand)','Hard_coal_-_final_consumption_(Metric_tons,_thousand)','Hard_coal_-_stock_changes_(Metric_tons,_thousand)','Hard_coal_-_transformation_in_electricity_plants_-_autoproducers_(Metric_tons,_thousand)','Hard_coal_-_consumption_by_transport_(Metric_tons,_thousand)','Hard_coal_-_consumption_by_rail_(Metric_tons,_thousand)','Hrad_coal_-_consumption_by_iron_and_steel_industry_(Metric_tons,_thousand)', 'Hard_coal_-_losses_(Metric_tons,_thousand)', 'Hard_coal_-_total_energy_supply_(Metric_tons,_thousand)']

UNES_HARD_COAL_BR.drop(ll, axis=1, inplace=True)

pandas: Extracting specific selected columns from a DataFrame to new DataFrame

【问题讨论】：

你可以使用df = df.iloc[:, [1,2,3,18]]

标签： python pandas

【解决方案1】：

使用.iloc[] 并注意pandas 从0 开始计算列：

In [14]: UNES_HARD_COAL_BR = UNES_HARD_COAL_BR.iloc[:, [0,1,2,17]]

In [15]: UNES_HARD_COAL_BR.head()
Out[15]:
            Hard_coal_-_production_(Metric_tons,_thousand)  \
Date
1990-12-31                                          4595.0
1991-12-31                                          5188.0
1992-12-31                                          4731.0
1993-12-31                                          4595.0
1994-12-31                                          5134.0

            Hard_coal_-_imports_(Metric_tons,_thousand)  \
Date
1990-12-31                                      10146.0
1991-12-31                                      10758.0
1992-12-31                                      10399.0
1993-12-31                                      10975.0
1994-12-31                                      11319.0

            Hard_coal_-_exports_(Metric_tons,_thousand)  \
Date
1990-12-31                                          NaN
1991-12-31                                          NaN
1992-12-31                                          NaN
1993-12-31                                          NaN
1994-12-31                                          NaN

            Hard_coal_-_consumption_by_chemical_and_petrochemical_industry_(Metric_tons,_thousand)
Date
1990-12-31                                              260.0
1991-12-31                                              375.0
1992-12-31                                              390.0
1993-12-31                                              362.0
1994-12-31                                              354.0

【讨论】：

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