dict comprehension python

A dictionary is another variable container model and can store any type of object. Each key value (Key=>value) pair of the dictionary is separated by a colon (:), separated by commas (,), and the entire dictionary is enclosed in curly braces ({}) ; The dictionary value can be used without restrictions on any Python object, either a standard object or a user-defined one, but the key is not available, and if the same key is assigned two times, the latte

Chapter 5-dict objects Similar to the map of C ++ STL in Python, dict is a ing container (key-> value), but the implementation principle is different. Because python uses a large number of structures such as dict (such as the Intese mechanism of string objects) and has high

The Python dictionary has three constructors, Dict (), Dict (**args), dict (mapping), and the first and second constructors are better understood and easier to use.The use of the dict (mapping) constructor is more difficult to understand.1

In python, there is a module collections, which is interpreted as a data-type container module. A collections. defaultdict () is frequently used. Let's talk about this. Summary: HereDefaultdict (function_factory)Build a similarDictionary, WhereKeysValue, which is determined by yourself,ValuesIsFunction_factoryAnd has the default value. For exampleDefault (INT)CreateDictionaryObject, anyValuesAllIntAnd even if it does not existKey,D [Key]There i

If you want to save one by one of the corresponding type of data, you can use Dict to indicate that all the data in the Dict are key-value pairs.First, create dict (Create Dict with {})Features of Dict:(1) The elements in the dict

3, Del d[' a '] #删除键值为 ' a ' element Traversing elements For K in D: print ' d[%s]= '% k,d[k] Or For k,v in D.items (): print ' d[%s]= '% k,v Or For k,v in D.iteritems (): print ' d[%s]= '% k,v Or For k,v in D.viewitems (): print ' d[%s]= '% k,v Items (), Iteritems () and viewitems () differences Python2.x's items () is a list that contains all the elements of dict, like the one above, but because of this too much memory, it was later added (note:

Many of the dict methods are similar to the list, with one by one below and a comparison with the list. Nesting Nested in the list also exists, that is, the element is a list, in the dict, there are similar styles: >>> a_list = [[1,2,3],[4,5],[6,7]]>>> a_list[1][1]5>>> a_dict = {1:{"name": "Qiwsir"},2: " Python "," email ":" qiwsir@gmail.com "}>>> a_dict{1: {'

A dictionary is the only type of mapping in the Python language. A hash value (key, key) and a pointing object (value, value) in a mapped type object are a one-to-many relationship that is often considered a mutable hash table. The object of the dictionary is mutable, which is a container type that can store any number of Python objects, which can also include other container types. The data in the dictiona