Attribute Error

I get the following attribution error:

AttributeError Traceback (most recent call last)
[](https://localhost:8080/#) in ()
4 for i in range(rebalance_window+validation_window, len(unique_trade_date)+1,rebalance_window):
5 temp = pd.read_csv('results/account_value_trade_{}_{}.csv'.format('ensemble',i))
----> 6 df_account_value = df_account_value.append(temp,ignore_index=True)
7 sharpe=(252**0.5)*df_account_value.account_value.pct_change(1).mean()/df_account_value.account_value.pct_change(1).std()
8 print('Sharpe Ratio: ',sharpe)

[/usr/local/lib/python3.10/site-packages/pandas/core/generic.py](https://localhost:8080/#) in __getattr__(self, name)
6291 ):
6292 return self[name]
-> 6293 return object.__getattribute__(self, name)
6294
6295 @final

AttributeError: 'DataFrame' object has no attribute 'append'

**Desktop (please complete the following information):**
- OS: Windows 10
- Browser: bing
-