将 Pandas 中的列转换为特定格式的日期时间

Question

I have the following code:

import pandas as pd
import datetime
df = pd.read_html("https://en.wikipedia.org/wiki/List_of_presidents_of_the_United_States")[1]
df = df[:-1]
df.rename(columns={'Presidency[a].1':"Term"}, inplace = True)
df[['Start', 'End']] = df.Term.str.split("–", expand = True)
df['Start'] = pd.to_datetime(df['Start'].str.strip(), format = '%B %d, %Y', dayfirst = False)

When i run this code I get the following error:

ValueError: unconverted data remains: [i]

Please advise

Answer 1

When I checked the data, it has some noisy entries like:

 'March 4, 1913',
 'March 4, 1913',
 'March 4, 1921',
 'August 2, 1923[r]',
 'August 2, 1923[r]',

You will have to clear them by splitting over df.Start = pd.Series([i.split('[')[0] for i in df.Start.tolist()])

Then it should work fine. See the output:

In [28]: df.Start = pd.to_datetime(df['Start'].str.strip(), format = '%B %d, %Y', dayfirst = False)

In [29]: df.Start
Out[29]: 
0    1789-04-30
1    1789-04-30
2    1797-03-04

Answer 2

Or just...

df.Start = df.Start.str.split("[", expand=True)

before converting to datetime

Answer 3

Several of the dates had annotations such as [i] at the end of the string.

The following uses pandas string replacement with a regular expression to remove the problematic annotations.

df['Start'] = pd.to_datetime(df['Start'].str.replace("\\[[az]\\]", "", regex=True))