The difference between python lists and dictionaries

List

1. An ordered collection of arbitrary objects

A list is a set of any Type of values, combined in a certain order

2. Read through offset

The values ​​that make up the list are called elements (Elements). Each element is marked with an index, the first index is 0, and the functions of the sequence can be realized

3. Variable length, heterogeneous and arbitrary nesting

Elements in the list can It is any type, even a list type, which means that lists can be nested

4. Variable sequences

support indexing, slicing, merging, deletion and other operations, they are all in the original Modify the list

5. Object reference array

The list can be treated as an ordinary array. Whenever a reference is used, Python will always point the reference to an object, so the program only needs Operations that handle objects. When assigning an object to a data structure element or variable name, Python always stores a reference to the object, rather than a copy of the object

Dictionary

1 .Read by key instead of offset

The dictionary is an associative array, a collection of objects indexed by keywords, stored using key-value, and the search speed is fast

2. An unordered collection of arbitrary objects

The items in the dictionary have no specific order, symbolized by "keys"

3. Variable length, heterogeneous , Arbitrary nesting

Same as list, nesting can include lists and other dictionaries, etc.

4. Belongs to variable mapping type

Because it is unordered, it cannot be performed Sequence operations, but can be modified remotely, by mapping keys to values. Dictionaries are the only built-in mapping type (objects that map keys to values)

5. Object reference table

Dictionaries store object references, not copies, just like lists. The key of the dictionary cannot be changed, and the list cannot be used as the key. Strings, primitives, integers, etc. can be compared

with the list. The dict has the following characteristics:

1. The speed of search and insertion is extremely fast and will not increase with the increase of key

2. It takes up a lot of memory and wastes a lot of memory

The opposite is true for list:

1. The time for searching and inserting increases as the number of elements increases

2. It occupies a small space and wastes very little memory

So, dict uses space in exchange for time. Method

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