Python (8) related dictionaries

The dictionaries in Python are completely different. They are not sequences, they are not ordered, but a ing. The internal elements are separated by commas (,).

. They are stored through keys instead of locations. They are also changeable and can be changed, increased, or decreased locally.

Main attributes:

<1> Read data by key instead of offset

<2> unordered set of any object

<3> variable length, heterogeneous, and arbitrary nesting

<4> variable ing

<5> Object Reference Table

Common Operations

D = {} empty dictionary

'Name' in D member existence Test

D. keys () method: Key

D. values () Value

D. items () Key + Value

D. copy () copy

D. get (key, default) default

D. update (D1) Merge

D. pop (key) Deletion

Len (D) evaluate the length

D [name] = 'ww 'modify and add

Del D [key] Delete

List (D. values () list (D. items () list (D. keys () converts the value to list

Ing operation

>>> D = {}

>>> D ['name'] = 'bob'

>>> D ['job'] = 'dev'

>>> D ['age'] = 40

>>> D

{'Age': 40, 'job': 'dev', 'name': 'bob '}

>>> Print (D ['name'])

Bob

Traversal

Since there is no order, we can first convert the dictionary key to list, sort and print.

>>> D = list (D. keys ())

>>> D

['A', 'C', 'B']

>>> D. sort ()

>>> D

['A', 'B', 'C']

>>> For I in d:

Print (I, '=>', d [I])

A => 1

B => 2

C => 3

Simplified point

>>> For key in sorted (D ):

Print (key, '=>', D [key])

Usage notes:

<1> the sequence operation is invalid (no sequence)

<2> assign a value to the new index to add an item.

<3> keys are not always strings.

<4> avoid missing key errors

Reference < >