identicallist

A mutable Python list that allows only identical objects and inherits their properties and methods.

If a list property changes, it changes this property in all items. If a list method is invoked, it invokes the method on all items.

Examples

IdenticalList behaves just like a list:

from identicallist import IdenticalList


class DummyItem:
    def __init__(self):
        self.num = 5

    def inc(self):
        self.num += 1

    def dec(self):
        self.num -= 1


il = IdenticalList(DummyItem(), DummyItem())
print(len(il)) # 2
print(iter(il)) # <generator object Sequence.__iter__ at 0x7fc3b708d5d0>
for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 5
# item number 1 has the attribute num with value 5

At the same time, it also behaves like the first object of the list:

print(il.num) # 5
il.inc()
print(il.num) # 6

Changing properties and calling methods on the list object affects all items in the list:

for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 6
# item number 1 has the attribute num with value 6
il.dec()
il.dec()
print(il.num) # 4
for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 4
# item number 1 has the attribute num with value 4
il.num = 7
for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 7
# item number 1 has the attribute num with value 7

Changing properties on individual items in the list only affect that item:

il[1].num = 8
for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 7
# item number 1 has the attribute num with value 8
il[0].dec()
for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 6
# item number 1 has the attribute num with value 8

Now, calling inc on the list increases all item's num property. Note that because they started with different values, the resulting values are still different:

il.inc()
for i, item in enumerate(il):
    print('item number {} has the attribute num with value {}'.format(i, item.num))
# item number 0 has the attribute num with value 7
# item number 1 has the attribute num with value 9