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A snippet of Python code with keywords highlighted in bold yellow font. The syntax of the Python programming language is the set of rules that defines how a Python program will be written and interpreted (by both the runtime system and by human readers). The Python language has many similarities to Perl, C, and Java. However, there are some ...
In such situations, all or part of the data model may be expressed as a collection of 2-tuples in the form <attribute name, value> with each element being an attribute–value pair. Depending on the particular application and the implementation chosen by programmers, attribute names may or may not be unique.
Some languages, such as Go, F# and Python, combine parallel assignment, tuples, and automatic tuple unpacking to allow multiple return values from a single function, as in this Python example, def f (): return 1 , 2 a , b = f ()
Python's tuple assignment, fully available in its foreach loop, also makes it trivial to iterate on (key, value) pairs in dictionaries: for key , value in some_dict . items (): # Direct iteration on a dict iterates on its keys # Do stuff
An n-tuple is a tuple of n elements, where n is a non-negative integer. There is only one 0-tuple, called the empty tuple. A 1-tuple and a 2-tuple are commonly called a singleton and an ordered pair, respectively. The term "infinite tuple" is occasionally used for "infinite sequences".
For returning multiple values from a function, an alternative is to return a tuple. Syntactically this is clearer if automatic sequence unpacking and parallel assignment can be used, as in Go or Python, such as:
The unpack operator will propagate the forwarding syntax to each parameter. This particular factory function automatically wraps the allocated memory in a std::shared_ptr for a degree of safety with regard to memory leaks. Additionally, the number of arguments in a template parameter pack can be determined as follows:
Returning a tuple of values. This is conventional in languages (such as Python) that have a built-in tuple data type and special syntax for handling these: in Python, x, y = f() calls the function f returning a pair of values and assigns the elements of the pair to two variables. Secondary return values as in Common Lisp. All expressions have a ...