Python 3.x-使用来自另一个datafram的列名创建dataframe

Question

Dataframe df1包含具有列名的字段“Column headers”。我想创建另一个数据帧df2，它只包含df1的“column headers”列中的列标题。

print(df1['Column header'])
>>
0                                              % Female
1                                  % Below poverty line
2                                    % Rural population
3                      Decadal Population Growth (in %)
4     Availability of Drinking Water Source Within P...
5                                 Concrete Roofs (in %)
6                        Houses With Electricity (in %)
7                        Houses With Televisions (in %)
8                           With Computer/Laptop (in %)
9        Houses With Phones (Telephone + Mobile) (in %)
10                        Houses With 2 wheelers (in %)
11                              Houses With cars (in %)
12              Households With Banking Services (in %)
13                                 Literacy Rate (in %)
14                         Literacy Rate (Rural) (in %)
15                         Literacy Rate (Urban) (in %)
16                  Decadal Difference In Literacy Rate
17                 Student: Teacher Ratio - All Schools
18                     Student: Teacher Ratio - Primary
19               Student: Teacher Ratio - Upper Primary
20     Under-five Mortality Rate (Per 1000 live Births)
21           No of Dispensaries per 1,00,000 population
22                No of Doctors per 1,00,000 population
23    Total patients registered for tuberculosis tre...
24                   Sex Ratio (Females Per 1000 Males)
25                                        Agri GSDP (%)
26                                    Industry GSDP (%)
27                                     Service GSDP (%)
28                        Unemployment Rate   (2011-12)
29                   Rural Unemployment Rate  (2011-12)
30                   Urban Unemployment Rate  (2011-12)
31                Per Capita Public Expenditure (in Rs)
32               Per Capita Private Expenditure (in Rs)
33                          Infant Mortality Rate (IMR)
34                             Maternal Mortality Rate 
35          Coverage Of National Highways (Total in km)
36             Coverage Of State Highways (Total in km)
37                Coverage Of Rural Roads (Total in km)
38                Coverage Of Urban Roads (Total in km)
39                       Railway Coverage (Total in km)
40    Tele-Density [Total Connections /  Total Popul...
Name: Column headers, dtype: object

我想创建包含40列的数据帧df2，如前所述。此数据框中的行将由另一个函数填充。 我试图创建df2如下-

df2 = pd.DataFrame()  #Creating an empty dataframe 
df2.columns = df1['Column header']
>>
ValueError: Length mismatch: Expected axis has 0 elements, new values have 41 elements

是否可以在Pandas中创建一个空白数据框，然后指定列名？

Answer 1

以下是如何创建具有自定义列的空数据框：

// Example dataframe
df1 = pd.DataFrame({"Headers": ["Alpha","Beta", "Gama", "Delta"]]}, columns=["Headers"], index=range(4))

print(df1)
//      Headers
//   0  Alpha
//   1  Beta
//   2  Gama
//   3  Delta


print(df1['Headers'].values)
// ['Alpha' 'Beta' 'Gama' 'Delta']

// Make empty dataframe, key here is index=None
df2 = pd.DataFrame({}, columns=df1['Headers'].values, index=None)

print(df2)    
// Empty DataFrame
// Columns: [Alpha, Beta, Gama, Delta]
// Index: []

Answer 2

试试这个：

df2 = pd.DataFrame(columns=df1['Column header'])

但不应该创建空的df，因为逐行填充它们非常慢。所以您应该先收集数据，然后使用预收集的数据创建DF。