为什么不应该在 python 中动态生成变量名? [英] Why shouldn't one dynamically generate variable names in python?

问题描述

现在我正在学习 Python 并在一些 OOP 概念上苦苦挣扎，其中之一是(对我而言)动态初始化类实例并将它们分配给动态生成的变量名是多么困难，以及我为什么要阅读我一开始就不应该那样做.

在大多数具有类似方向的线程中，答案似乎是这样做是非 Pythonic 的.

例如在python中动态生成变量名

有人能详细说明一下吗?

以典型的 OOP 学习案例为例:

LOE = ["graham", "eric", "terry_G", "terry_J", "john", "carol"]类员工():def __init__(self, name, job="喜剧演员"):self.name = 姓名self.job = 工作

为什么这样做更好:

employees = []LOE 中的名称:emp = 员工(姓名)员工.追加(emp)

然后

对于雇员中的emp:如果 emp.name == "eric":打印(emp.job)

代替这个

对于 LOE 中的名称:globals()[name] = Employee(name)

和

print(eric.job)

谢谢！

解决方案

如果动态生成变量名，不知道存在哪些名称，也无法在代码中使用.

globals()[some_unknown_name] = Foo()

好吧，现在呢?你不能安全地这样做:

eric.bar()

因为你不知道 eric 是否存在.无论如何，您最终都必须使用字典/列表来测试 eric 是否存在:

if 'eric' in globals(): ...

因此，只需将您的对象存储在字典或列表中即可:

people = {}人['eric'] = Foo()

通过这种方式，您还可以安全地迭代一个数据结构来访问所有分组的对象，而无需从其他全局变量中对它们进行排序.

Right now I am learning Python and struggling with a few concepts of OOP, one of that being how difficult it is (to me) to dynamically initialize class instances and assign them to a dynamically generated variable name and why I am reading that I shouldn't do that in the first place.

In most threads with a similar direction, the answer seems to be that it is un-Pythonic to do that.

For example generating variable names on fly in python

Could someone please elaborate?

Take the typical OOP learning case:

LOE = ["graham", "eric", "terry_G", "terry_J", "john", "carol"]
class Employee():
    def __init__(self, name, job="comedian"):
        self.name = name
        self.job = job

Why is it better to do this:

employees = []
for name in LOE:
    emp = Employee(name)
    employees.append(emp)

and then

for emp in employees:
    if emp.name == "eric":
        print(emp.job)

instead of this

for name in LOE:
    globals()[name] = Employee(name)

and

print(eric.job)

Thanks!

解决方案

If you dynamically generate variable names, you don't know what names exist, and you can't use them in code.

globals()[some_unknown_name] = Foo()

Well, now what? You can't safely do this:

eric.bar()

Because you don't know whether eric exists. You'll end up having to test for eric's existence using dictionaries/lists anyway:

if 'eric' in globals(): ...

So just store your objects in a dictionary or list to begin with:

people = {}
people['eric'] = Foo()

This way you can also safely iterate one data structure to access all your grouped objects without needing to sort them from other global variables.

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