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Why python want us this : Non-default argument follows default argument [closed]

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class Node():
def __init__(self,value,parrent=None,neigh) -> None:
self.val=value
self.parrent=parrent
self.neigh=neigh
Here I want to define a class. There is an error about neigh that non-default argument follows default argument. I saw the solution of this question but my main question is I want to know why python want us to do this?

Because Python allows omission of keyword / default-specified parameters and allows passing parameters without explicitly naming them. If your definition was legal syntax (and the rest of the language functioned the same way), then instantiating
n = Node(4, 6)
might mean either
n = Node(value=4, parrent=6, neigh=None)
or
n = Node(value=4, parrent=None, neigh=6)
The point of syntax rules is to resolve ambiguities like this.

Not Match Between Argument Passed and List Available [closed]

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I was working with Python3, and trying some sorts of code. And then i came to try some function features, here is my code
def print_list_members(some_list):
for i in first_list:
print(i)
that's all my function definition. and then i add for example new to the code
first_list = ["Alfried", "Michael", "John"]
second_list = ["Joseph", "Tim", "Delta"]
then i try to produce traceback by passing different argument with the function code
print_list_members(second_list)
but, no traceback raised, except something make me a bit confused, the output is
Alfried
Michael
John
the question is, how it be possible? or is it an error from python itself?

Change your code here
def print_list_members(some_list):
for i in some_list:
print(i)

You iterate over the global first_list inside the body of the function, so you print first_list. Whatever you pass as an argument is ignored. Perhaps you wanted iterate over some_list?

Passing a string to eval in method [closed]

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Struggling with passing a variable reference to a nested function. Using a dictionary is not an option in my use case. It's a much simplified MRE (real use passes an object with many nested objects).
def func(reference):
eval('trueVal=' + reference)
print(trueVal) #Expecting trueVal=15000
trueValue = 15000
reference = 'trueValue'
func(reference)

eval evaluates expressions. The result of your expression in your example can then be assigned to trueVal explicitly:
trueVal = eval(reference)

I would not endorse using eval or exec, 99 times out of 100, there is a better way to do it, dictionary is not the only option but without posting your question its impossible to provide a better way to approach it. below is for reference as an example that works without hardcoding the variable name. But really there is always likely a better approach thatn eval or exec.
def func(reference, value):
exec(reference + '="' + str(value) +'"')
print(reference, ":", eval(reference)) #Expecting trueVal=15000
trueValue = 15000
reference = 'trueVal'
func(reference, trueValue)

Re-usable function [closed]

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I am using Python for some operations on a XML file.
Because I am new to programming I would like to know how I can re-use the snippet below, currently it has a hard-coded statement in it.
Please look at the line with
for ERPRecord in aroot.iter('part'):
inside it, aroot should be replaced with the modular option or variable.
def SetERP(ArticleN,ERPn):
for ERPRecord in aroot.iter('part'):
if ERPRecord.get('P_ARTICLE_ORDERNR') == ArticleN:
ERPRecord.set('P_ARTICLE_ERPNR', ERPn)
I would like to have a function without hard-coded parts in so it is able to be used again in other projects. My best guess is that the sequence "aroot" will be replaced by a variable like this:
def SetERP(ArticleN,ERPn, XMLroot):
for ERPRecord in XMLroot.iter('part'):
if ERPRecord.get('P_ARTICLE_ORDERNR') == ArticleN:
ERPRecord.set('P_ARTICLE_ERPNR', ERPn)
Any advice on this would be welcome!

You could define aroot as a parameter, so you would have to pass your root in every time you call the function, if that is what you mean?
def SetERP(ArticleN, ERPn, aroot):
for ERPRecord in aroot.iter('part'):
if ERPRecord.get('P_ARTICLE_ORDERNR') == ArticleN:
ERPRecord.set('P_ARTICLE_ERPNR', ERPn)

Access value of function attribute in python [closed]

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Suppose I have a function -
def foo(x,y):
pass
a = foo(5,6)
How do I access the values 5 and 6 from a?

From the code you have shown us, you cannot -- 5 and 6 were passed in to foo, you didn't keep a copy of them, foo didn't keep a copy of them, so they are gone.
So, as the above paragraph hinted, somebody has to keep a copy of those arguments if you want to do something else with them later, and while it is possible to have a function do so, that's not really what they are intended for. So your easy options are:
make foo a class that saves the arguments it was called with (which is still highly unusual), or
save the arguments yourself (arg1, arg2 = 5, 6 for example)

You can't. You'd need to use an object.