Python basic tuple (tuple), dictionary (Dictionary) detailed

Tuple definition

A tuple is another data type, similar to a list.
The tuple is identified with a "()". The inner elements are separated by commas. However, an element cannot be assigned two times, which is equivalent to a read-only list.

Example:
tuple = (' ABCD ', 786, 2.23, ' John ', 70.2)

list = [' ABCD ', 786, 2.23, ' John ', 70.2]

Tuple[2] = 1000 # tuples are illegal to apply

List[2] = 1000 # is a legitimate application in the list

Print tuple * 2 # output tuple two times

Dictionary definitions

The Dictionary (dictionary) is the most flexible built-in data structure type in Python, except for lists. A list is an ordered combination of objects, and a dictionary is a collection of unordered objects.

The difference between a list and a dictionary is that the elements in the dictionary are accessed by keys, not by offsets.
The dictionary is identified with "{}". A dictionary consists of an index (key) and a value corresponding to it.
{key1:value1, key2:value2, ..., Keyn:valuen}
Dictionaries are also referred to as associative arrays or hash tables.

Two things to note in a dictionary:
1, the keys in the dictionary must be unique, but the value is not necessary. When created, if the same key is assigned two times, the old value is replaced;
2, the key must be immutable, can be used as a number, string or tuple, but can not use the list

Create a dictionary

(1) Factory method

Adict = Dict () or

Adict = Dict (([' X ', 1],[' Y ', 2]))

(2) Keyword parameters

adict= dict (name= ' Allen ', age= ' 40′)

(3) Built-in method

L1 = [D.fromkeys] (L1)

Dict.fromkeys (L1, ' over ') {1: "Over", 2: ' Over ', 3: ' Over '}

B={}.fromkeys ((' x ', ' Y '), 1)

Update dictionary Operations

Adict[new_key] = value form adds an item

Adict[old_key] = new_value Update a data item (element) or key-value pair

del Adict[key] Delete keys key

Del adict Delete entire dictionary

Dictionary Common Methods

1, Adict.keys () returns a list containing all keys of the dictionary;

2, Adict.values () returns a list containing all the value of the dictionary;

3, adict.clear () Delete all the items or elements in the dictionary;

4, Adict.get (key, default = None) returns the value corresponding to the key in the dictionary, and returns the value of default if the key does not exist in the dictionary (default defaults to none);

5, Adict.pop (Key[,default]) is similar to the Get method. If there is a key in the dictionary, delete and return the key corresponding to the Vuale; if the key does not exist and the default value is not given, the keyerror exception is thrown;

6, Adict.update (bdict) Add dictionary bdict key value pairs to the dictionary adict, none Add, there is overwrite

Example:
Adict={1: ' A ', 2: ' B ', 3: ' C '}
Bdict={1: ' AA ', 5: ' CCC ', 8: ' 66 '}

Adict.update (bdict)
Print Adict

For key in Adict.keys ():

print key

For value in Adict.values ():

print value

For Key,value in Adict.items ():

print str(key)+‘:‘+str(value)

Python basic tuple (tuple), dictionary (Dictionary) detailed