求助：修正Python代码，生成各列含4个无重复值的DataFrame

Let's break down what's going wrong with your current code first:

In your nested loops, every time you iterate through a value in cal, you're overwriting the value of dict[i] with the latest calculation. By the end of the loops, each column key in your dictionary only holds the result from the last j value (13), which is why you're not getting the 4 rows of data you expect.

Here's the corrected code that will generate a DataFrame with 4 rows (one for each value in cal) and 4 columns (one for each entry in col):

import pandas as pd

def newtable():
    # Avoid using 'dict' as a variable name—it's a built-in Python type!
    data_dict = {}
    col = ['DAYS','VWAP','TURNOVER','DEL_QTY']
    cal = [3,5,8,13]
    
    # Initialize an empty list for each column to store all 4 calculation results
    for column in col:
        data_dict[column] = []
    
    # Loop through each calculation period first
    for j in cal:
        # Calculate the value for each column at this period and add to the list
        for column in col:
            # Get the first j rows of the target column, sum them, then divide by j
            column_index = final_3.columns.get_loc(column)
            value = final_3.iloc[:j, column_index].sum() / j
            data_dict[column].append(value)
    
    # Create the DataFrame, using 'cal' as the index to show which period each row corresponds to
    result_df = pd.DataFrame(data_dict, index=cal)
    print(result_df)

Key Improvements: #

• Variable Name Fix: Swapped dict for data_dict to prevent overriding Python's built-in dictionary type.
• List Initialization: Each column starts with an empty list, so we can append all 4 period results instead of overwriting a single value.
• Loop Order Adjustment: We iterate through periods first, then columns, ensuring every period's calculation is captured for each column.
• Clear Index: Using cal as the DataFrame index makes it easy to see which calculation period each row represents.

内容的提问来源于stack exchange，提问作者jacky