功能前的变量分配

Question

我创建了一个使用pandas和xlsxwriter快速转换数据的包。 这非常有效，我成功地完成了一些功能。 但最近我碰到了一堵墙：

对于一些函数，我需要首先定义变量，但它们不是基本类型（list，tuple，str等），而是例如数据帧。 我查看了全局变量并看到它们没有被推荐（并且不知道放在哪里）我也看了上课但我不知道如何使用它们来解决我的问题。 我也试过创建一个空的数据帧，但在函数后得到一个空的数据帧。

我正在尝试做的是一个带有pandas for .csv或.xlsx的读取函数和一个用Xlsxwriter引擎保存的函数。 目标是在代码中尽可能少地进行更改，以便经常快速地转换数据（例如，我的函数执行LEFT，RIGHT就像在Excel中一样，甚至是带有列号的MIDDLE），并且在main.py中有一个简单的代码。

这是我的代码的精简版本，它使用2个python文件（main.py和format_operations.py）。 我添加了评论，我遇到了问题。 在此先感谢您的帮助！

    """ 
    main.py
    """
    import format_operations as tbfrm #import another python file in the same folder
    import pandas as pd
    import numpy as np
    import xlsxwriter.utility

    #file settings
    file_full_path= "C:/Tests/big_data.xlsx"
    file_save_to= "C:/Tests/Xlsxwriter.xlsx"
    sheet_name_save_to= "Xlswriter"
    dfname = ??? #I need to create the variable but I don't know how
    tbfrm.FCT_universal_read(dfname,file_full_path) #CAN'T GET IT TO WORK

    #column operations and formatting
    columns_numeric = [3,6] # (with pandas) list of columns with number values by iloc number, starts at 0 which is column A in Excel
    tbfrm.FCT_columns_numeric(dfname,columns_numeric) #example of a WORKING function (if dfname is defined)

    #write with Xlsxwriter engine
    XLWRITER_DF = ??? #same problem as before, how to create the variable?
    workbookvarname = ??? #same here
    worksheetvarname = ??? # same here
    tbfrm.FCT_df_xlsxwriter(XLWRITER_DF,dfname,file_save_to,sheet_name_save_to,workbookvarname,worksheetvarname) #CAN'T GET IT TO WORK

    #### WORKING piece of code I want to execute after saving with Xlsxwriter engine ####
    worksheet.set_zoom(80)

    # Conditional formatting
    color_range_1 = "J1:J{}".format(number_rows+1)
    FORMAT1 = workbook.add_format({'bg_color': '#FFC7CE','font_color': '#9C0006'})
    FORMAT2 = workbook.add_format({'bg_color': '#C6EFCE','font_color': '#006100'})
    worksheet.conditional_format(color_range_1, {'type': 'bottom','value': '5','format': FORMAT1})
    worksheet.conditional_format(color_range_1, {'type': 'top','value': '5','format': FORMAT2})

其他档案：

    """ 
    format_operations.py
    """
    import pandas as pd
    import numpy as np
    import xlsxwriter.utility

    def FCT_universal_read(dfname,file_full_path):
        if ".xls" in file_full_path:
            dfname = pd.read_excel(file_full_path) #optional arguments:sheetname='Sheet1', header=0 , dtype=object to preserve values
        if ".csv" in file_full_path:
            dfname = pd.read_csv(file_full_path)

    # save file with XLSXWriter engine for additional options to pandas
    def FCT_df_xlsxwriter(XLWRITER_DF,dfname,file_save_to,sheet_name_save_to,workbookvarname,worksheetvarname):
        XLWRITER_DF = pd.ExcelWriter(file_save_to, engine='xlsxwriter')
        dfname.to_excel(XLWRITER_DF, sheet_name=sheet_name_save_to,encoding='utf-8')
        workbookvarname = XLWRITER_DF.book
        worksheetvarname = XLWRITER_DF.sheets[sheet_name_save_to]

    #format as numbers
    def FCT_columns_numeric(dfname,columns_numeric):
        for x in columns_numeric:
            dfname.iloc[:,x] = pd.to_numeric(dfname.iloc[:,x])

Answer 1

您的FCT_universal_read函数不应修改数据框，而是返回一个新数据框：

def FCT_universal_read(file_full_path):
    if file_full_path.split('.')[-1] == "xls":
        df = pd.read_excel(file_full_path) #optional arguments:sheetname='Sheet1', header=0 , dtype=object to preserve values
    if file_full_path.split('.')[-1] == "csv":
        df = pd.read_csv(file_full_path)
    return df

在你的主要，做：

dfname = tbfrm.FCT_universal_read(file_full_path)

FCT_df_xlsxwriter的答案相同，您应该使用返回值重写它，以便您可以执行以下操作：

    XLWRITER_DF, workbookvarname,worksheetvarname =  tbfrm.FCT_df_xlsxwriter(dfname,file_save_to,sheet_name_save_to) 

要了解python如何处理传递给函数的参数，您应该阅读以下博客文章：

https://jeffknupp.com/blog/2012/11/13/is-python-callbyvalue-or-callbyreference-neither/ https://robertheaton.com/2014/02/09/pythons-pass-by-object-参考作为说明的逐菲利普-K-迪克/

Answer 2

您需要更新FCT_universal_read以便返回所需的数据帧。 无需在函数外部定义数据框，只需创建并返回它即可

df = FCT_universal_read('/your/file/path')

def FCT_universal_read(file_full_path):
        if ".xls" in file_full_path:
            df = pd.read_excel(file_full_path) #optional arguments:sheetname='Sheet1', header=0 , dtype=object to preserve values
            return df
        if ".csv" in file_full_path:
            df = pd.read_csv(file_full_path)
            return df

Answer 3

非常感谢你们两个！ 我现在得到了逻辑:)！ 还要感谢文档。

我成功地完成了这两项功能。 我一直在挣扎几个小时。 我喜欢你使用的.split函数，它确保脚本只查看扩展名。

我按照你的说法更新了FCT_xlsxwriter和FCT_universal_read。 以下两个功能都已更正：

    '''
    format_operations.py
    '''
    def FCT_universal_read(file_full_path):
        if "xls" in file_full_path.split('.')[-1]:
            dfname = pd.read_excel(file_full_path) #example: C:/Tests/Bigdata.xlsx
            return dfname
        if "csv" in file_full_path.split('.')[-1]:
            dfname = pd.read_csv(file_full_path)
            return dfname


    def FCT_df_xlsxwriter(dfname,file_save_to,sheet_name_save_to):
        XLWRITER_DF = pd.ExcelWriter(file_save_to, engine='xlsxwriter')
        dfname.to_excel(XLWRITER_DF, sheet_name=sheet_name_save_to,encoding='utf-8')
        workbook = XLWRITER_DF.book
        worksheet = XLWRITER_DF.sheets[sheet_name_save_to]
        return XLWRITER_DF,workbook,worksheet

以下是我如何调用这两个函数：

    '''
    main.py
    '''

    import format_operations as tbfrm
    import pandas as pd
    import xlsxwriter.utility

    #settings
    file_full_path= "C:/Tests/big_data.xlsx"
    file_save_to= "C:/Tests/Xlsxwriter.xlsx"
    sheet_name_save_to= "Xlswriter"

    #functions
    FILE_DF = tbfrm.FCT_universal_read(file_full_path)
    XLWRITER_DF,workbook,worksheet = tbfrm.FCT_df_xlsxwriter(FILE_DF,file_save_to,sheet_name_save_to)