How to append a modified list into a list?

[Ian Kelly]

On Nov 18, 2016 6:47 PM, <jfong at ms4.hinet.net> wrote:

I have a working list 'tbl' and recording list 'm'. I want to append 'tbl'
into 'm' each time when the 'tbl' was modified. I will record the change by
append it through the function 'apl'.

For example:

>>>tbl=[0,0]
>>>m=[]

>>>tbl[0]=1
>>>apl(tbl)
>>>m
[[1,0]]

>>>tbl[1]=2
>>>apl(tbl)
>>>m
[[1,0], [1,2]]

How to define this function properly?

Obviously the most intuitive way doesn't work.
def apl0(tbl):
    m.append(tbl)

and introducing a local variable will not help either.
def apl1(tbl):
    w=tbl
    m.append(w)

I figure out a workable way, but looks ugly.
def apl2(tbl):
    w=[]
    w[:]=tbl
    m.append(w)

I know those binding tricks between names and objects. Just wondering if
there is an elegant way of doing this:-)


The important thing is to copy the list, not rebind it.

def apl(tbl):
    m.append(tbl[:])

Or:

def apl(tbl):
    m.append(list(tbl))