У меня есть фрейм данных с колонкой под названием"Date" и хотите, чтобы все значения в этом столбце имели одинаковое значение (только год). Пример:

City     Date
Paris    01/04/2004
Lisbon   01/09/2004
Madrid   2004
Pekin    31/2004

Что я хочу это:

City     Date
Paris    2004
Lisbon   2004
Madrid   2004
Pekin    2004

Вот мой код:

fr61_70xls = pd.ExcelFile('AMADEUS FRANCE 1961-1970.xlsx')

#Here we import the individual sheets and clean the sheets    
years=(['1961','1962','1963','1964','1965','1966','1967','1968','1969','1970'])

fr={}

header=(['City','Country','NACE','Cons','Last_year','Op_Rev_EUR_Last_avail_yr','BvD_Indep_Indic','GUO_Name','Legal_status','Date_of_incorporation','Legal_status_date'])

for year in years:
    # save every sheet in variable fr['1961'], fr['1962'] and so on
    fr[year]=fr61_70xls.parse(year,header=0,parse_cols=10)
    fr[year].columns=header
    # drop the entire Legal status date column
    fr[year]=fr[year].drop(['Legal_status_date','Date_of_incorporation'],axis=1)
    # drop every row where GUO Name is empty
    fr[year]=fr[year].dropna(axis=0,how='all',subset=[['GUO_Name']])
    fr[year]=fr[year].set_index(['GUO_Name','Date_of_incorporation'])

It happens that in my DataFrames, called for example fr['1961'] the values of Date_of_incorporation can be anything (strings, integer, and so on), so maybe it would be best to completely erase this column and then attach another column with only the year to the DataFrames?