Pandas 对Excel的同一个sheet表多次写入，不覆盖数据。

在我的这篇博客里 https://blog.youkuaiyun.com/Matrix_cc/article/details/105025330 讲述了pandas处理Excel的一些基本的读写操作。

今天来个稍微高级点。

向Excel的同一个sheet表里写入的话，pandas没有现成的API使我们调用，所以需要我们自己定义一个函数：

import pandas as pd
from openpyxl import load_workbook

def append_df_to_excel(filename, df, sheet_name='Sheet1', startrow=None,
                       truncate_sheet=False,
                       **to_excel_kwargs):
    """
    Append a DataFrame [df] to existing Excel file [filename]
    into [sheet_name] Sheet.
    If [filename] doesn't exist, then this function will create it.
    Parameters:
      filename : File path or existing ExcelWriter
                 (Example: '/path/to/file.xlsx')
      df : dataframe to save to workbook
      sheet_name : Name of sheet which will contain DataFrame.
                   (default: 'Sheet1')
      startrow : upper left cell row to dump data frame.
                 Per default (startrow=None) calculate the last row
                 in the existing DF and write to the next row...
      truncate_sheet : truncate (remove and recreate) [sheet_name]
                       before writing DataFrame to Excel file
      to_excel_kwargs : arguments which will be passed to `DataFrame.to_excel()`
                        [can be dictionary]
    Returns: None
    """
    # from openpyxl import load_workbook

    # import pandas as pd

    # ignore [engine] parameter if it was passed
    if 'engine' in to_excel_kwargs:
        to_excel_kwargs.pop('engine')

    writer = pd.ExcelWriter(filename, engine='openpyxl')

    # Python 2.x: define [FileNotFoundError] exception if it doesn't exist
    try:
        FileNotFoundError
    except NameError:
        FileNotFoundError = IOError

    try:
        # try to open an existing workbook
        writer.book = load_workbook(filename)

        # get the last row in the existing Excel sheet
        # if it was not specified explicitly
        if startrow is None and sheet_name in writer.book.sheetnames:
            startrow = writer.book[sheet_name].max_row

        # truncate sheet
        if truncate_sheet and sheet_name in writer.book.sheetnames:
            # index of [sheet_name] sheet
            idx = writer.book.sheetnames.index(sheet_name)
            # remove [sheet_name]
            writer.book.remove(writer.book.worksheets[idx])
            # create an empty sheet [sheet_name] using old index
            writer.book.create_sheet(sheet_name, idx)

        # copy existing sheets
        writer.sheets = {ws.title: ws for ws in writer.book.worksheets}
    except FileNotFoundError:
        # file does not exist yet, we will create it
        pass

    if startrow is None:
        startrow = 0

    # write out the new sheet
    df.to_excel(writer, sheet_name, startrow=startrow, **to_excel_kwargs)

    # save the workbook
    writer.save()

然后我们就可以调用了，注意！在调用时，要调整 startcol 这个参数，要不然它会把前面一列的数据给覆盖掉。

fw = pd.DataFrame({'A':[1,2]})

fw1 = pd.DataFrame({'B':[3,4]})

fw2 = pd.DataFrame({'C':[5,6]})

append_df_to_excel(target_path,fw,sheet_name='Sheet1', startcol=0,startrow=0,index=False)

append_df_to_excel(target_path,fw1,sheet_name='Sheet1', startcol=1,startrow=0,index=False)

append_df_to_excel(target_path,fw2,sheet_name='Sheet1', startcol=2,startrow=0,index=False)

在运行时，如果这个Excel文件存在，它可能会报 zipfile.BadZipFile: File is not a zip file 这个错误，我们只需要把这个Excel文件删除就可以了，而且不要在文件打开的时候进行写入，这样会报权限不允许的错误！

参考：

https://stackoverflow.com/questions/20219254/how-to-write-to-an-existing-excel-file-without-overwriting-data-using-pandas/20221655#