Use this tag for questions related with argument unpacking, a technique that allows Arrays and Traversable objects to be extracted/unpacked into argument lists/sequences.
argument-unpacking is usually found in PHP, Python and Go.
Questions tagged [argument-unpacking]
144 questions
1
vote
2 answers
python tuples: unpacking into a list using *args
Hello and thanks for your time;
I am using *args to take various arguments, which creates a tuple. How do I 'unpack' a tuple into a list? The following code appends the list with a tuple.
grades = []
def add_grades(*args):
…
JulienEast
- 27
- 7
1
vote
0 answers
Space in unpacked keywords does not lead to syntax error
When handling connection string attributes, I noticed a curious behavior in Python's argument unpacking. Passing in an argument that has spaces in the name works.
def f(**kwargs):
print(kwargs)
f(spaced keyword=3) # Syntax…
Felix
- 2,548
- 19
- 48
1
vote
1 answer
Python- Unpack A List in Pandas Slicer
I wrote a function that does something similar like following. The function expects a multi-level dataframe. column_name argument can be ['Deal Name','Deal Expense']. To filter a multi-level dataframe, I would need to unpack the column_name list…
Aaron Lin
- 41
- 4
1
vote
1 answer
Iteratively unpack function output - error: too many values to unpack
I wrote a function which returns different outputs and I need to iteratively call the function for each element of an array (passed as an iterable).
However, I am only able to retrieve the output as a tuple and I can't figure out how to unpack each…
CAPSLOCK
- 6,243
- 3
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- 56
1
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0 answers
Does unpacking sequences [strings, lists] and sets involve casting into a tuple?
I just learnt of unpacking with the * and so went on some test runs. I realized that although some write about passing in tuples as arguments in place of positional arguments, I could also pass in strings, lists and sets and Python wouldn't complain…
heretoinfinity
- 1,528
- 3
- 14
- 33
1
vote
1 answer
Iterating through elements of variable arguments
I have a function scalar_func(*args) that takes a variable number scalar numbers. It preforms some math with them and outputs a scalar. As a trivial example, we'll assume scalar_func multiplies each number:
def scalar_func(*args):
out = 1
…
user276833
- 77
- 6
1
vote
1 answer
Unpack tuple to member initialization or superclass constructor
Is it possible to initialize a member of a class (or call superclass constructor) by using the arguments contained in a tuple?
Please note that I am aware of std::make_from_tuple() and std::apply() but they cannot be used in this scenario.
Consider…
barsdeveloper
- 930
- 8
- 28
1
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1 answer
named tuple from dictionary using double-star-operator: are nested fields unpacked too?
I have two classes: Top and Nested, and to create both of them I need to provide TopDefinition and NestedDefinition objects, which are of type NamedTuple (definitions are required for type annotations). And Class Top contains attribute, which is a…
John Overiron
- 517
- 1
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- 20
1
vote
1 answer
how to remove padding in struct python during unpacking
When I use packing in struct, I find out that during unpacking that I have extra characters after I unpack the byte object.
For example before packing:
c = b'CONNECT'
value gotten after unpacking using struct is b'CONNECT\x00\x00\x00\x00\x00'
Here…
Francis
- 61
- 1
- 4
1
vote
2 answers
How to remove/ignore unexpected keyword arguments when passing as dictionary?
The following code
def f(par1, par2):
print("par1 = %s, par2 = %s" % (str(par1), str(par2)))
pars = {
'par1': 12,
'par2': 13,
'par3': 14
}
f(**pars)
raises error
TypeError: f() got an unexpected keyword argument 'par3'
How to…
Dims
- 47,675
- 117
- 331
- 600
1
vote
2 answers
How to unpack a list of lists?
This may be a duplicate question, but I want to find out is there a way to unpack a list of lists and make a variable from an unpacked result? I have a data in the file like:
'[416213688, 422393399, 190690902, 81688],| [94925847, 61605626,…
NagaevAF
- 21
- 1
- 4
1
vote
0 answers
Strange unpacking of a custom dictionary / mapping in Jython
I have run into a strange dictionary / mapping unpacking behavior in Jython. Originally, in the context of SQLAlchemy, but I managed to narrow it down to the following minimal example:
import collections
class…
Leonid Shifrin
- 22,449
- 4
- 68
- 100
1
vote
3 answers
Unpacking argument in print statements
I would like to know if there is a way to unpack values in a print statement, the same way it is possible to unpack arguments in a function f
This works:
import numpy
er = numpy.array([0.36666667, 0.46666667, 0.43333333, numpy.nan])
l =…
Nuageux
- 1,668
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- 17
- 29
1
vote
2 answers
TypeError: cannot do slice indexing on with these indexers [(2,)] of
I've a user defined function as follows:-
def genre(option,option_type,*limit):
option_based = rank_data.loc[rank_data[option] == option_type]
top_option_based = option_based[:limit]
print(top_option_based)
…
Nayana Madhu
- 1,185
- 5
- 17
- 34
1
vote
2 answers
Get first item of returning function value
I'm working with kinterbasdb module, and the module has this function called fetchone, that returns the result of an execution of a query:
cursor.execute("....")
cursor.fetchone()
This returns a tuple: ("value1",), and i want access the first item,…
user7427352