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Can anyone explain the reason why python behaves differently in the following two cases please? Much appreciation.
def modifyNone(x):
print("B4:"+str(x))
# x.append(5)
x=[5]
print("In:"+str(x))
a = []
modifyNone(a)
print("After:"+str(a))
Output:
B4:[]
In:[5]
After:[]
Method:
def modifyNone(x):
print("B4:"+str(x))
x.append(5)
# x=[5]
print("In:"+str(x))
a = []
modifyNone(a)
print("After:"+str(a))
Output:
B4:[]
In:[5]
After:[5]
Python is pass by value, so you'll have to reassign a returned value like so:
a = modifyNone(a) # where the function returns a value
You don't seem to understand variable scope as well, try the documentation.
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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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How do I get the returned result from the below function?
def various_return_types(n):
if(n==1):
return True
else:
return False
various_return_types(1)
The function call does return a value but since you are not assigning it to a variable, you can't use it.
If you use
ret = various_return_types(1)
then, ret will contain the boolean value you can check.
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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)
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In the following Python code, what does the (x) mean?
Dropout(0.8)(x)
(x) uses the preceding function reference (returned by Dropout(0.8)) to make a function call with x as the argument.
For example:
def Dropout(a):
def func(b):
return a + b
return func
x = 0.2
print(Dropout(0.8)(x))
would output 1.0.
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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.