Is it possible to unpack a tuple in Python without creating unwanted variables?
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Is there a way to write the following function so that my IDE doesn't complain that column is an unused variable?
def get_selected_index(self): (path, column) = self._tree_view.get_cursor() return path
In this case I don't care about the second item in the tuple and just want to discard the reference to it when it is unpacked.
In Python the
_ is often used as an ignored placeholder.
(path, _) = self._treeView.get_cursor()
You could also avoid unpacking as a tuple is indexable.
def get_selected_index(self): return self._treeView.get_cursor()
Unpacking in Python: Beyond Parallel Assignment, Multiple assignment (also known as tuple unpacking or iterable of items and that it works with variables as well as objects we've just created: We're just not doing an unnecessary extra assignment in the first example. Python unpack tuple example Any sequence (or iterable) can be unpacked into variables using a simple assignment operation. The only requirement is that the number of variables and structure match the sequence .
If you don't care about the second item, why not just extract the first one:
def get_selected_index(self): path = self._treeView.get_cursor() return path
Multiple assignment and tuple unpacking improve Python code , Python tuples are immutable means that they can not be modified in whole program. Packing In other way it is called unpacking of a tuple of values into a variable. In python tuples can be unpacked using a function in function tuple is passed and in function values are unpacked into normal variable. A tuple is created. Write a Python program to unpack a tuple in several variables. There was a problem connecting to the server. Please check your connection and try running the trinket again. It looks like you haven't tried running your new code. Try clicking Run and if you like the result, try sharing again. Resetting will undo all of your current changes.
Yes, it is possible. The accepted answer with
_ convention still unpacks, just to a placeholder variable.
You can avoid this via
from itertools import islice values = (i for i in range(2)) res = next(islice(values, 1, None)) # 1
This will give the same
res as below:
_, res = values
The solution, as demonstrated above, works when
values is an iterable that is not an indexable collection such as
Unpacking a Tuple in Python, Created: 02-Mar-2007 Tuple parameter unpacking is the use of a tuple as a parameter in a function to unpack to variables spam and monty (meaning it is the tuple (spam, Bytecode analysis is how the inspect.getargspec function is able to (an otherwise unneeded burden as all other types of parameters do not This lesson will teach you about unpacking tuples. What Is a Tuple? A tuple is an immutable ordered list of objects. It can contain references to any type of object. See Learn to Program Using Python: Empty and Single-Item Tuples for a more detailed description. Sample Program Unpacking a tuple. Listing 1 shows the beginning of a Python script
it looks pretty, I don't know if a good performance.
a = (1, 2, 3, 4, 5) x, y = a[0:2]
PEP 3113 -- Removal of Tuple Parameter Unpacking, Basics of unpacking a tuple and a list Unpack a nested tuple and list An error occurs if the number of variables does not match the number of of variables is less than the number of elements, it is possible to add an By convention, unnecessary values may be assigned to underscores _ in Python. A tuple is just like a list of a sequence of immutable python objects. The difference between list and tuple is that list are declared in square brackets and can be changed while tuple is declared in parentheses and cannot be changed. However, you can take portions of existing tuples to make new tuples. Tuple Syntax.
Unpack a tuple / list in Python, Python can unpack any iterable object: a tuple, a list, a string, or an array. There are The other variables, x, y, and z, contain the individual components of the rotated vector. Unintended side effects on arrays can be particularly troublesome. Python does not automatically create a local copy of an array inside a function. Using Python, I unpack Tuple contents into the corresponding Lvalues, that is, the variables on the left of the assignment operator.
A Student's Guide to Python for Physical Modeling: Updated Edition, Python example to unpack tuple or sequence or iterable such that the tuple may be longer than N elements, causing a "too many values to unpack" exception. Unpack tuple and throw away unwanted values You can't just specify a bare * when unpacking, but you could use a common throwaway variable name, such as Varun August 5, 2018 Python Tuple: Different ways to create a tuple and Iterate over it 2018-08-05T09:41:09+05:30 Python, Tuple No Comment In this article we will discuss what is tuple, how its different from list, different ways to create a tuple and iterate over it.
Python unpack tuple - too many values to unpack, In this case, the fields variable in the recipe would be bound to a list of eight ints. Note that struct. unpack returns a tuple. Because A list is not immutable, so each field can be rebound as needed. Thus If you're creating the binary file from scratch but you still want to be able to reread and update some records Updating a The example above: article, noun, verb, adjective, direct_object = t is called "tuple unpacking" because the tuple t was unpacked and its values assigned to each of the variables on the left. "Tuple packing" is the reverse: t=article, noun, verb, adjective, direct_object.
- It's worth noting that
_is not any kind of syntactic magic, but a convention (of course, it's a convention recognised by IDEs and pylint, and Python conventions are pretty strong...)
- Python would be nothing without conventions!
- Is this convention documented?
- @Gaius: I believe in Haskell it explicitly means "discard this value"; in Python
_is still an assigned variable that you could in theory use just like any other variable.
- The python command line interpreter "magically" assigns _ to the result of the last computation so if you run something but forget to store the return value, it will be captured for you in the
_variable. It's a useful thing while doing interactive work. In the above case, I'd probably do indexing rather than unpacking though.
- Note that the return should now be
return path, not
- This is weaker, because it removes the assertion that there are exactly two items.
- @Michael Mior: I've rolled back your edit: Based on the original question, it should still be
pathseems to be a sequence itself)
- I'd argue that this is less explicit as the _ placeholder convention. There's potential ambiguity in the order of operations, is it:
(path = self._treeView.get_cursor())or
path = (self._treeView.get_cursor())