如何將一列的Pandas數據框轉換為兩列的Pandas數據框？

Question

我有一個只有一欄的數據框，其中包含各州及其后面的特定區域。 狀態已經按字母順序排列。 我想將此單列轉換為兩列。

import pandas as pd
places = [{'State':'Alabama'},{'State':'Auburn'},{'State':'Florence'},{'State':'Troy'},{'State':'Alaska'},{'State':'Fairbanks}]
df0 = pd.DataFrame(places)

s1 = df0.loc[df['State']=='Alabama'].index[0] #return row of state 'Alabama'
s2 = df0.loc[df['State']=='Alaska'].index[0]  #return row of state 'Alaska'
df1 = df0                                     # create new dataframe

for index, row in df0.iterrows():             # parse single column into two columns data
    if index == s1:
        df1['State']='Alabama'
    elif index <= s2:
        df1['Region']=row['State']
df

上面的代碼返回：

     State    Region
0    Alabama   Alabama
1    Alabama   Alabama
...  ...       ...
500  Alabama   Alabama

注意：在我的示例中，我僅使用阿拉巴馬州和阿拉斯加，但其他州在此下方還有500行。 任何想法我如何可以做到以下幾點：

     State     Region
0    Alabama   Auburn
1    Alabama   Florence
2    Alabama   Troy
3    Alaska    Fairbanks
...  ...       ...

Answer 1

首先，您需要擁有狀態的所有數據：下載並調用狀態會很好。 我將嘗試在前幾行中手動調用它

#This is not necessary. Download the file and call states directly from it.
import re
import pandas as pd
a = 'http://code.activestate.com/recipes/577305-python-dictionary-of-us-states-and-territories/download/1/'
states = eval(re.sub("(?<=\w')\s+(?=[^:])",",","".join(['{']+list(pd.read_csv(a).index))))

只需按原樣運行此代碼，然后執行print(states)查看IDE中是否具有所有狀態。也可以從此處直接復制粘貼為states

現在我們有了所有狀態，就可以解決問題

import numpy as np

places = [{'State':'Alabama'},{'State':'Auburn'},{'State':'Florence'},{'State':'Troy'},{'State':'Alaska'},{'State':'Fairbanks'}]

df0 = pd.DataFrame(places)
df0['Regions'] = df0.State

B = pd.DataFrame(df0.set_index('Regions').State.replace(regex=f'^(?!({"|".join(states.values())})).*',value=np.nan).reset_index()).ffill()
B[B.State!=B.Regions].iloc[:,[1,0]]

     State    Regions
1  Alabama     Auburn
2  Alabama   Florence
3  Alabama       Troy
5   Alaska  Fairbanks