如何在python中将文件路径设置为全局变量？

Question

我一直收到这个错误NameError: name 'filep' is not defined我需要将filep作为文件路径。但每次我运行我的代码，我总是得到这个错误

我需要将filep作为模块变量，而不是参数和menulist

import csv

filep= # filepath
menulist = [] #global scope


def menu_List():

    global menulist 
    menulist = []  # store items
    try:
        with open(filep) as f:  # read file
            reader = f.readlines()
            next(reader, None) #skip the header

            for row in reader:
                row[2] = int(row[2].strip()) #convert string to int
                row[1] = float(row[1].strip()) #convert string to float
                if row[2] > 100 and row[2] < 200:
                    menulist.append(row)
    except NameError:
        raise ValueError("Variable not set")

    menulist.sort(key=lambda x: x[-1])

menu_List()

Answer 1

这里不需要全局变量，函数应该接受路径作为参数并返回菜单列表

import csv

def menu_List(filep):

    menulist = []  # store items
    try:
        with open(filep) as f:  # read file
            reader = f.readlines()
            next(reader, None) #skip the header

            for row in reader:
                row[2] = int(row[2].strip()) #convert string to int
                row[1] = float(row[1].strip()) #convert string to float
                if row[2] > 100 and row[2] < 200:
                    menulist.append(row)
    except NameError:
        raise ValueError("Variable not set")

    menulist.sort(key=lambda x: x[-1])
    return menulist

menulist = menu_List("a/path/goes/here")

与您的问题无关，您可以像这样跳过标题：

reader = f.readlines()
for row in reader[1:]: # skip the first line.
    ...

Answer 2

上面的答案（对fliep使用args）是最好的解决方案，但如果您决定不使用args：

filep= 'file path you want'# filepath
menulist = [] #global scope


def menu_List():
    global filep #just add one more global will make it work
    global menulist 
    menulist = []  # store items
    try:
        with open(filep) as f:  # read file
            reader = f.readlines()
            next(reader, None) #skip the header

            for row in reader:
                row[2] = int(row[2].strip()) #convert string to int
                row[1] = float(row[1].strip()) #convert string to float
                if row[2] > 100 and row[2] < 200:
                    menulist.append(row)
    except NameError:
        raise ValueError("Variable not set")

    menulist.sort(key=lambda x: x[-1])

menu_List()

额外小贴士：尽可能避免使用全局变量，全局变量会降低程序的速度并消耗内存，有时还会导致变量命名混乱