Python parsing of various operations, and parsing of mathematical concepts What is the connection?

Parsing in python

Python supports a variety of analytical (comprehension) operation, such as a list comprehension, a collection of analytical, analytical tuples, dictionaries resolution. They create (derive) a new list, set of tuples, dictionaries according to certain elements. It is sometimes called derivation, such as a list comprehension, collection derivations.

Here is an example of a list comprehension:

1 >>> [ i*2 for i in range(10) if i % 2 == 0 ]
2 [0, 4, 8, 12, 16]

Here is a list of resolution because brackets [XXXX] used, it represents a new list is derived according to the conditions. Several built-in types in Python parsing rules:

• If you are using square brackets to indicate a list comprehension
• If you are using braces, it represents the set of analytic
• If you are using braces, and which elements are key: value mode, parsing the dictionary

Note: If you are using parentheses represents the generator expressions, rather than analytical.

E.g:

1 # 集合解析
2 >>> { i*2 for i in "abcd"}
3 {'aa', 'cc', 'dd', 'bb'}
4
5 # 字典解析
6 >>> { k:v for k,v in zip(("one","two","three"),(1,2,3)) }
7 {'one': 1, 'two': 2, 'three': 3}
8 >>> { k: k*2 for k in "abcd" }
9 {'a': 'aa', 'b': 'bb', 'c': 'cc', 'd': 'dd'}
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Of course, Python there are other parsing scheme.

Analytical mathematical concept of

Analytical computer language from the set of mathematical concepts described (corresponding to the set resolution). As shown below:

This corresponds to the following list for analysis:

[ i * 2 for i in range(10) if i % 2 == 0 ]

among them:

• x ∈ N represents the element of containers, the container element is iterated objects parsed
• This corresponds to a range (10) in the list of parsed for Python, as long as the data objects is iterative, may be provided as a container element
• x is a variable, a container element
• Corresponding to the list of analytical i
• x²> 3 is represented by predicates conditional formula is optional, the parsing process for screening qualifying element
• This corresponds to the list of parsed if i% 2 == 0, note that the predicate part is optional
• 2 * x represents the external expression, the elements used to generate a new list / set / dictionary / tuple
• Corresponding to the list of analytical i * 2
• {} Means that the expression of outer container element is stored in a collection container
• Parsing the list corresponding to [], the newly generated element is represented in the list of elements

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