Create a new column in a dataframe based on a date-CodePudding

I’m new in python and I would like to add a column based on a date with several condition. My data came from a sheet.

Currently my code looks like this :

#Save data in a DataFrame

df1 = pd.read_excel(stream_io1, sheet_name = "Sheet1", header=0)

# Use Accounting Date 
df1['Item - Accounting Date'] = pd.to_datetime(df1['Item - Accounting Date'], format='%Y-%m-%d')

def condition(row):
    if (row['Item - Accounting Date'] < '2020-01-01') in row['Item - Accounting Date']:
        return "<2020"
    if "2020" in row['Item - Accounting Date']:
        return "2020"
    if (row[(row['Item - Accounting Date'] >= "01/01/2021") & (row['Item - Accounting Date'] <="30/06/2021")]) in row['Item - Accounting Date']:
        return "S1 2021"    
    if (row[(row['Item - Accounting Date'] > "30/06/2021") & (row['Item - Accounting Date'] <="31/12/2021")]) in row['Item - Accounting Date']:
        return "S2 2021" 

df1['Année'] = df1.apply(condition, axis = 1)

And I have this error message :

TypeError: '<' not supported between instances of 'Timestamp' and 'str'

I understand the error but I don’t know how to resolve it

CodePudding user response：

from datetime import datetime
datetime.strptime("2020-01-01","%Y-%m-%d")

this is how you can convert string to datetime object

CodePudding user response：

It appears you only need to apply condition function to one column, so you can fix it as below using pd.to_datetime:

def condition(row):
    if row < pd.Timestamp('2020-01-01'):
        return "<2020"
    if "2020" in row:
        return "2020"
    if (row >= pd.Timestamp("2021-01-01")) & (row <=pd.Timestamp("2021-06-30")):
        return "S1 2021"    
    if (row > pd.Timestamp("2021-06-30")) & (row <=pd.Timestamp("2021-12-31")):
        return "S2 2021" 

df1['Année'] = df1['Item - Accounting Date'].apply(condition)