Pandas (Python) - Problem appending list to empty dataframe with column names

The pandas documentation reads

DataFrame.append(other, ignore_index=False, verify_integrity=False, sort=None)

other : DataFrame or Series/dict-like object, or list of these The data to append.

So you need to have to transform your list prior to appending it to your DataFrame:

something that might work is to zip the list of your columns to the content of your myList so it would be:

tradeLog = pd.DataFrame(columns=["DATE", "TICKER", "ORDER_TYPE", "AMOUNT", "PRICE"])
myList = ['2018-01-12', 'MMM', 'BUY', 42, 236.5229]
myDict = dict(zip(tradeLog.columns.tolist(), myList))

tradeLog.append(myDict, ignore_index=True)

or tradeLog.append(pd.DataFrame(myDict), ignore_index=True)

This being said you need to ensure your lists are always the same length as your columns names list.

DataFrame.append() is for appending rows from an other pandas dataframe or series (see the docs).

So, if it is absolutely necessary to do this line by line, you can

tradeLog = tradeLog.append(pd.Series(myList, index=tradeLog.columns), ignore_index=True)

(N.b.: tradeLog.loc[len(tradeLog)] = ... appends to the end only as long as you have a simple integer index on tradeLog, but might break for more complex use cases.)

You might also want to consider this remark from the docs:

Iteratively appending rows to a DataFrame can be more computationally intensive than a single concatenate. A better solution is to append those rows to a list and then concatenate the list with the original DataFrame all at once.