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--- python3_unpacking [2018/08/06 10:11]
jguerin [Explicit Unpacking: The * (Star) Operator]
+++ — (current)
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-====== Unpacking Sequences ======
-Sequences can be explicitly/implicitly //unpacked// into discrete, ordered units of some type. Unpacking happens automatically using the '','' (comma). (The syntax is also used for [[python3_tuples|Tuple]] construction.)
-Unpacking works //only// in instances where the number of variables used //exactly// matches the number of items in the sequence.
-In the below examples parenthesis are not required, and are included for clarity.
-=====Implicit Unpacking: Member Assignment=====
-The most common application of unpacking is to (shallow) copy items into named variables.
-====Lists====
-Unpacking a [[python3_lists|List]].
-<code python>
->>> seq = [1, 2, 3]
->>> (a, b, c) = seq  # a=1, b=2, c=3
-</code>
-====Tuples====
-Unpacking a [[python3_tuples|Tuple]].
-<code python>
->>> tup = ('a', 'b')
->>> (x, y) = tup # x='a', y='b'
-</code>
-====Strings====
-Unpacking the characters of a [[python3_strings|String]].
-<code python>
->>> (fst, snd, thd) = "abc" # fst='a', snd='b', thd='c'
-</code>
-=====In-Place Swap/Mutual Replacement=====
-Swapping objects.
-<code python>
->>> x = 1
->>> y = 2
->>> (x, y) = (y, x) # x=2, y=1
-</code>
-=====Explicit Unpacking: The * (Star) Operator=====
-The unary ''*'' (star) operator is used to explicitly indicate unpacking, often outside the context of assignment. Use is common when elements of a sequence are intended to be used as the parameters to a function.
-E.g., (Assume that ''seq'' contains 3 elements) ''fun(seq[0], seq[1], seq[2])'' could be rephrased more tersely as ''fun(*seq)''.
-====Unpacking Arguments====
-<code python>
->>> print([1, 2, 3]) # legal, but performs a cast str([1, 2, 3])
-[1, 2, 3]
-</code>
-<code python>
->>> print(*[1, 2, 3]) # as though we indexed each individually
-2 3
-</code>
-<code python>
-</code>
-====Extended Iterable Unpacking====

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