pandas 将数据框列名称从字符串格式更改为日期时间
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Change dataframe column names from string format to datetime
提问by gtroupis
I have a dataframe where the names of the columns are dates (Year-month) in the form of strings. How can I convert these names in datetime format? I tried doing this:
我有一个数据框，其中列的名称是字符串形式的日期（年-月）。如何将这些名称转换为日期时间格式？我试过这样做：
new_cols = pd.to_datetime(df.columns)
df = df[new_cols]
but I get the error:
但我收到错误：
KeyError: "DatetimeIndex(
['2000-01-01', '2000-02-01',
'2000-03-01', '2000-04-01',
'2000-05-01', '2000-06-01',
'2000-07-01', '2000-08-01',
'2000-09-01', '2000-10-01',
'2015-11-01', '2015-12-01',
'2016-01-01', '2016-02-01',
'2016-03-01', '2016-04-01',
'2016-05-01', '2016-06-01',
'2016-07-01', '2016-08-01'],
dtype='datetime64[ns]', length=200, freq=None) not in index"
Thanks!
谢谢！
回答by jezrael
If select by loccolumns values was not changed, so get KeyError.
如果按loc列选择值未更改，则获取KeyError.
So you need assign output to columns:
所以你需要将输出分配给columns：
df.columns = pd.to_datetime(df.columns)
Sample:
样本：
cols = ['2000-01-01', '2000-02-01', '2000-03-01', '2000-04-01', '2000-05-01']
vals = np.arange(5)
df = pd.DataFrame(columns = cols, data=[vals])
print (df)
2000-01-01 2000-02-01 2000-03-01 2000-04-01 2000-05-01
0 0 1 2 3 4
print (df.columns)
Index(['2000-01-01', '2000-02-01', '2000-03-01', '2000-04-01', '2000-05-01'], dtype='object')
df.columns = pd.to_datetime(df.columns)
print (df.columns)
DatetimeIndex(['2000-01-01', '2000-02-01', '2000-03-01', '2000-04-01',
'2000-05-01'],
dtype='datetime64[ns]', freq=None)
Also is possible convert to period:
也可以转换为句点：
print (df.columns)
Index(['2000-01-01', '2000-02-01', '2000-03-01', '2000-04-01', '2000-05-01'], dtype='object')
df.columns = pd.to_datetime(df.columns).to_period('M')
print (df.columns)
PeriodIndex(['2000-01', '2000-02', '2000-03', '2000-04', '2000-05'],
dtype='period[M]', freq='M')
回答by Fred Cascarini
As an expansion to jezrael's answer, the original code will be trying to slice the df array by the array stored in new_cols and store the result as df - but since those values don't exist in df yet it returns an error saying it can't find that index to slice by.
作为对 jezrael 答案的扩展，原始代码将尝试通过存储在 new_cols 中的数组对 df 数组进行切片并将结果存储为 df - 但由于这些值在 df 中不存在但它返回一个错误，表示它可以' t 找到要切片的索引。
As such you need to declare that you're changing the name of the columns, as in jezrael's answer.
因此，您需要声明您正在更改列的名称，如 jezrael 的回答。
