如何使用参数中带有关键字“self”的 Python 函数
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how to use a Python function with keyword "self" in arguments
提问by imoum
i have a function that retrieve a list of stores in Python this functions is called :
我有一个在 Python 中检索商店列表的函数，这个函数被称为：
class LeclercScraper(BaseScraper):
"""
This class allows scraping of Leclerc Drive website. It is the entry point for dataretrieval.
"""
def __init__(self):
LeclercDatabaseHelper = LeclercParser
super(LeclercScraper, self).__init__('http://www.leclercdrive.fr/', LeclercCrawler, LeclercParser, LeclercDatabaseHelper)
def get_list_stores(self, code):
"""
This method gets a list of stores given an area code
Input :
- code (string): from '01' to '95'
Output :
- stores :
[{
'name': '...',
'url'
}]
"""
when i try to write get_list_stores(92)i get this error :
当我尝试编写时，出现get_list_stores(92)此错误：
get_list_stores(92)
TypeError: get_list_stores() takes exactly 2 arguments (1 given)
how can you help me with this ?
你怎么能帮我解决这个问题？
采纳答案by óscar López
If the function is insidea class (a method), write it like this:
如果函数在一个类（一个方法）中，写成这样：
def get_list_stores(self, code):
And you have to call it over an instance of the class:
您必须通过类的实例调用它：
ls = LeclercScraper()
ls.get_list_stores(92)
If it's outside a class, write it without the selfparameter:
如果它在类之外，则不带self参数写入：
def get_list_stores(code):
Now it can be called as a normal function (notice that we're not calling the function over an instance, and it's no longer a method):
现在它可以作为普通函数调用（注意我们不是通过实例调用函数，它不再是方法）：
get_list_stores(92)
回答by jsbueno
You don't use "self" arbitrarily - self is recommended to be the first parameter to functions which are written to be methods in classes. In that case, when it is invoked as a method, like in
不要随意使用“self” - 建议将 self 作为编写为类中方法的函数的第一个参数。在这种情况下，当它作为方法被调用时，就像在
class A(object):
def get_list_stores(self, code):
...
a = A()
a.get_listscores(92)
Python will insert the "self" parameter automatically on the call (and it will be the object named "a" in the outer scope)
Python 将在调用时自动插入“self”参数（它将是外部作用域中名为“a”的对象）
Outside of class definitions, having a first parameter named "self" does not make much sense - although, as it is not a keyword it is not an error per se.
在类定义之外，将第一个参数命名为“self”并没有多大意义——尽管它不是关键字，因此本身并不是错误。
In your case, most likely,t he function you are trying to call is defined in class: you have to call it as an attribute of an instance of the class, and then you simply omit the first parameter - just like in the example above.
在您的情况下，您尝试调用的函数很可能是在类中定义的：您必须将其作为类实例的属性调用，然后您只需省略第一个参数 - 就像上面的示例一样.
回答by óscar López
If you are trying to use it in the class, access it like this:
如果您尝试在课堂上使用它，请像这样访问它：
self.get_listscores(92)
If you are trying to access it outside of the class, you need to first create an instance of LeclercScraper:
如果您试图在类之外访问它，则需要首先创建一个实例LeclercScraper：
x = LeclercScraper()
y = x.get_listscores(92)
Also, selfis not a keyword. It is simply the name chosen by convention to represent a class instance within itself.
此外，self不是关键字。它只是按照惯例选择的名称来表示其自身内的类实例。
Here's a good reference:
这是一个很好的参考：
