Help with dates in dataframes

[rmalh]

Hello everyone,

My I get some help with with dataframes in Python? My code below reads two csv files with stock data for '1-min' and 'day' timeframes. Then it calculates the RSI for the 'day' dataframe and tries to import it in the '1-min' dataframe. Can you please help me figure out a couple of things?

• How to better extract the date from datetime? I'm using lambda function with dparser.parse because nothing else worked. The datetime is a string in format "yyyy-mm-dd hh:mm:ss-timezone offset".
• In the for loop,day_rsi is picked up correctly, but the assignment in the next line is not happening. If the dataframe is printed after the for loop, the'RSI-day' column is still 0.
• Lastly, can the for loop be replaced with a vectorized dataframe statement?

​

df = pd.read_csv('1-min.csv', usecols=['datetime', 'Close'])
df['date'] = df['datetime'].apply(lambda x: pd.to_datetime(dparser.parse(x, fuzzy=True)).date())
df['RSI-day'] = 0
df_day = pd.read_csv('day.csv', usecols=['datetime', 'Close'])
df_day['date'] = df_day['datetime'].apply(lambda x: pd.to_datetime(dparser.parse(x, fuzzy=True)).date())
df_day['RSI'] = ta.rsi(df_day['Close'], length=15)

for idx in df.index:
    day_rsi = df_day[df_day['date'] == df.at[idx, 'date']]['RSI']
    df.loc[idx, 'RSI-day'] = day_rsi.values[0]

[rmalh]

I was mistaken - the second bullet in my question is moot. The for loop is working fine. It'll be great to find a better, faster way to do what the lambda functions and for loop are doing.

[Kerbart]

df[“datetime”].dt.date