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我已经在 python3.8 中实现了一个可迭代的类，在这篇实现该函数的帖子之后weakref()，为了能够删除该类的元素，正如帖子接受的答案中所解释的那样。

问题是，如果我在函数中填充可迭代类，我将不再能够迭代其元素：

#! /usr/bin/env python3.8

import sys
import weakref
# from memory_profiler import profile

# IN = "/home/enrico/Dropbox/NY/asilo_variant/inputs/merged.idter_M.norm.PASS.filtered.head1k.VEPoutput.vcf"

a = [ "a", "b", "c", "d" ]

class VEPh_iterator(type):
    def __iter__(self):
        return self.classiter()

class VEPh:
    '''
        this stores VEP header and relative column numbers and chars
    '''
    __metaclass__ = VEPh_iterator
    by_id = {}

    def __init__(self, id, column_number):
        self.id = id
        # self.by_id[id] = self
        self.by_id[id] = weakref.ref(self)
        self.column_number = column_number

    @classmethod
    def classiter(cls):
        # return iter(cls.by_id.values())
        return (i for i in (i() for i in cls.by_id.values()) if i is not None)

def readVCF( ):
    name_dict = {}
    for i,s in enumerate(a) :
        name_dict.update({ i : s })
        name_dict[i] = VEPh( s, i )

if __name__ == "__main__" :
    readVCF( )
    for v in VEPh.classiter():
        print( "  -  " + v.id + " :    " + str(v.column_number) )

调用它有一个空的 OUT：

python3.8 /home/enrico/Dropbox/NY/asilo_variant/asilo_variant.stackoverflow.py

### NO STDOUT

如果修改删除weakref()它有效：

#! /usr/bin/env python3.8

import sys
import weakref
# from memory_profiler import profile

# IN = "/home/enrico/Dropbox/NY/asilo_variant/inputs/merged.idter_M.norm.PASS.filtered.head1k.VEPoutput.vcf"

a = [ "a", "b", "c", "d" ]

class VEPh_iterator(type):
    def __iter__(self):
        return self.classiter()

class VEPh:
    '''
        this stores VEP header and relative column numbers and chars
    '''
    __metaclass__ = VEPh_iterator
    by_id = {}

    def __init__(self, id, column_number):
        self.id = id
        self.by_id[id] = self
        # self.by_id[id] = weakref.ref(self)
        self.column_number = column_number

    @classmethod
    def classiter(cls):
        return iter(cls.by_id.values())
        # return (i for i in (i() for i in cls.by_id.values()) if i is not None)

def readVCF( ):
    name_dict = {}
    for i,s in enumerate(a) :
        name_dict.update({ i : s })
        name_dict[i] = VEPh( s, i )

if __name__ == "__main__" :
    readVCF( )
    for v in VEPh.classiter():
        print( "  -  " + v.id + " :    " + str(v.column_number) )

称它有效：

python3.8 /home/enrico/Dropbox/NY/asilo_variant/asilo_variant.stackoverflow.py 
  -  a :    0
  -  b :    1
  -  c :    2
  -  d :    3

我想问题是weakref()函数之间以某种方式丢失了，但是我怎样才能让它可以被外部函数调用呢？

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