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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.
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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.
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I tried searching online but did not find any answer to this particular question. In python there are no function declarations and a function can't be used until it has been defined.
Does this mean that indirect recursion is impossible in python?
And is there a way around this by using some modules?
No, it is possible
def f():
print('from f')
g()
def g():
print('from g')
f()
"a function can't be used until it has been defined" is not so straightforward. When the code runs, the name of the objects that it refers to have to exist. So, you can't do
f()
def f():...
because f() actually executes something. But definitions create a function object, without running it at the time. In the example, the function is claled at the last line of the script, and, by that time, both f, g do exist.
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I'm a novice python programmer and thinking this is a very simple task.
I'm trying to use a function argument as a value within a df variable when calling the function, but it is returning the argument address and not the argument value.
def func_name(var_name):
df['varname']=str(var_name)
func_name(split_rand)
df
I want varname to contain "split_rand" throughout, but it contains <function split_rand at 0x0000025E4EAD9A60>. I know that enclosing 'split_rand' in quotes will work, but I don't want to use that for alternative reasons.
Thank you
It's returning the string representation of that function name. If you want the actual function name, then you do func.__name__
I think you meant to do df['varname']=var_name.__name__ instead and I'd rename var_name to func.
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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?
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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)