argument-unpacking Questions
1
Solved
I want to define a concept in C++ (<= C++20) to check if a type matches any of the types define in a type-list struct.
The following is my attempt so far:
template<typename... Types>
struc...
Metencephalon asked 12/3 at 9:38
5
Solved
In code like zip(*x) or f(**k), what do the * and ** respectively mean? How does Python implement that behaviour, and what are the performance implications?
See also: Expanding tuples into argumen...
Friedrick asked 27/5, 2010 at 14:10
28
Solved
What do *args and **kwargs mean in these function definitions?
def foo(x, y, *args):
pass
def bar(x, y, **kwargs):
pass
See What do ** (double star/asterisk) and * (star/asterisk) mean in a fu...
Policewoman asked 31/8, 2008 at 15:4
3
Solved
I have two vectors:
std::vector<int> v1{ 1, 2, 3 };
std::vector<int> v2{ 4, 5, 6 };
I want to create an object of std::initializer_list which holds iterators to the first and last elem...
Program asked 10/7, 2023 at 11:15
6
Solved
I've been looking at passing arrays, or lists, as Python tends to call them, into a function.
I read something about using *args, such as:
def someFunc(*args)
for x in args
print x
But not su...
Godinez asked 18/10, 2010 at 16:8
4
Solved
Without subclassing dict, what would a class need to be considered a mapping so that it can be passed to a method with **.
from abc import ABCMeta
class uobj:
__metaclass__ = ABCMeta
uobj.regis...
Morrell asked 22/12, 2011 at 8:39
3
Solved
I'd like to make a class that unpacks it's objects like a dictionary.
For example, with a dictionary you can do this
foo = {
"a" : 1
"b" : 2
}
def bar(a,b):
return a +...
Koon asked 16/2, 2022 at 16:14
2
Solved
I know that the asterisk is used to unpack values like system args or when you unpack lists into variables.
But I have not seen this syntax here before in this example of asyncio.
I was reading thi...
Jeer asked 30/9, 2021 at 15:38
3
Solved
The error message is:
FATAL ERROR Uncaught Error: Cannot unpack array with string keys
I know I can simply run the method fetch() twice and pass the ['q'] and ['bind'], but I am trying to get to ...
Theona asked 17/11, 2016 at 19:42
3
Solved
I get an error type object argument after ** must be a mapping, not tuple.
I have this code:
create_character = player.Create(**generate_player.generate())
this is player.py module:
class Create...
Ludwig asked 11/4, 2014 at 10:18
4
Solved
Consider the following expressions. Note that some expressions are repeated to present the "context".
(this is a long list)
a, b = 1, 2 # simple sequence assignment
a, b = ['green', 'blue...
Mead asked 6/8, 2011 at 14:59
2
Solved
Example use:
def f(a, b, c, d):
print(a, b, c, d, sep = '&')
f(1,2,3,4)
>>> 1&2&3&4
f(*[1, 2, 3, 4])
>>> 1&2&3&4
Where in the python documentation...
Implead asked 23/9, 2012 at 19:38
1
Solved
In C++, if a function returns a std::pair<int, int>, we can auto-receive it as follows:
auto pr = some_function();
std::cout << pr.first << ' ' << pr.second;
Now, C++17 s...
Beora asked 7/5, 2020 at 15:28
2
Solved
As of PHP7.4, there is a newly available technique to re-index an array with numeric keys.
I'll call it "array re-packing" or maybe something fun like "splatpacking". The simple process involves u...
Sanative asked 30/8, 2019 at 11:21
5
Solved
I have a function definition as below and I am passing keyword arguments. How do I get to return a dictionary with the same name as the keyword arguments?
Manually I can do:
def generate_student_...
Bunnybunow asked 4/2, 2016 at 10:0
2
Consider a function defined as:
def fun(a, *args):
print(type(args), args)
When called, it packs the extra positional arguments as a tuple.
>>> fun(2, 3, 4)
<class 'tuple'> (3, ...
Daughterinlaw asked 16/12, 2019 at 15:50
1
Solved
def fun(a, b, c, d):
print('a:', a, 'b:', b, 'c:', c, 'd:', d)
why this one works
fun(3, 7, d=10, *(23,))
and prints out:
a: 3 b: 7 c: 23 d: 10
while this
fun(3, 7, c=10, *(23,))
does n...
Continuance asked 20/11, 2019 at 19:11
4
Solved
So in Python and Ruby there is the splat operator (*) for unpacking an array as arguments. In Javascript there is the .apply() function. Is there a way of unpacking an array/slice as function argum...
Kalila asked 9/7, 2013 at 18:45
3
Solved
If I have a NumPy array, for example 5x3, is there a way to unpack it column by column all at once to pass to a function rather than like this: my_func(arr[:, 0], arr[:, 1], arr[:, 2])?
Kind of l...
Moravia asked 20/11, 2014 at 18:7
3
In Python, by convention, the underscore (_) is often used to throw away parts of an unpacked tuple, like so
>>> tup = (1,2,3)
>>> meaningfulVariableName,_,_ = tup
>>> m...
Inhumation asked 4/12, 2017 at 21:51
4
Solved
Given a flat list of simple dictionaries
lst = [{'key1': 1}, {'key2': 2}, {'key3': 3}]
I'd like to find the dict that yields the minimum value evaluated using a method not detailed here.
My firs...
Cwmbran asked 21/9, 2017 at 13:53
1
Solved
The unpacking/splat operators * and ** differ widely in their applicability across python versions (2.7, 3.x < 3.5 and 3.x >= 3.5).
For example:
| 2.7 | 3.1-3.4 | 3.5
-----------------------...
Pilsen asked 27/7, 2017 at 9:5
1
Solved
I am trying in python to unpack some dict into some function:
I have a function that get packet as parameter (that should be dict)
def queue(self, packet):
self.topic.publish(self.message, self....
Cachinnate asked 10/7, 2017 at 14:25
3
Solved
I know what the meaning of an asterisk is in a function definition in Python.
I often, though, see asterisks for calls to functions with parameters like:
def foo(*args, **kwargs):
first_func(arg...
Gamin asked 3/7, 2015 at 2:37
1
Solved
I have data like data = [[t1, t2, ...], [v1, v2, ...]]. I want to wrap this in a class so I can call data.t instead of having to use data[0].
I tried to do this with the following:
class Variable...
Fahland asked 25/10, 2016 at 14:20
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