foo = ['amc', 'AAPL', 'gme', 'MSFT', 'TSLA']
dfs = [pd.read_csv(f'{x}.csv').assign(Name=x.upper()) for x in foo]
df = pd.concat(dfs).drop(columns=[ 'Open', 'High', 'Low'])

df['Close/Last']=df['Close/Last'].str.replace('$',"", regex=True).astype(float)


df['date']=pd.to_datetime(df['Date'])
df=df.sort_values(by=['Name', 'date'])

df=df.groupby(pd.PeriodIndex(df['date'], freq='M'))['Close/Last'].mean()

print(df),