Python Quick Start 02-0529

Data type conversions:

Show

Implicit

Dir (__builtin__) to view the built-in functions

Callable () can be used to test whether a function can be called

Dictionary: KV Set

{"A": +, "B": 545}

Each module has a built-in variable named __name__, which is adjusted to

If the module is imported, the value of __name__ is the module's name

If the module is executed directly, the value of __name__ is "__main__"

Class: Usually the custom type is used

Type: Built-in variable

Instance: instantiation

Classes: Data and methods

Data: Variables

Method: function

Classes: Instantiating objects

Comparison of two objects:

1. Value comparison: Whether the data in the object is the same

2. Identity comparison: Two variable names refer to the same object

3. Type comparison: Two objects are of the same type

Core data types

Numbers: Int,long,flocat,complex,bool

Character: Str,unicode

Listing: List

Dictionary: Dict

Tuples: Tuple

Files: File

Other types: Collection (set), Frozenset, class type, null (None)

Other file class tools: piping (pipes), FIFO (FIFOs), sockets

Type conversions:

STR (), repr (), and form

at (): Converts non-character data to characters

STR: The result of doing object serialization, casting

REPR: Do exact conversions, do not convert meta objects

Format

Int (): Convert to Integer

Float (): Convert to floating-point type

List (s): Convert string S to list

Tuple (s): convert string s to Narimoto group

Set (s): Converts a string s to a collection

Frozenset (s): Converts a string s to an immutable collection

Dict (d): Creates a dictionary based on the specified key-value pair, where D must be a tuple sequence (key,value)

Chr (x): Converts an integer to a character

Ord (x): Converts a character to an integer value

Hex (x): Converts an integer to 16 binary characters

Bin (x): Converts an integer to 2 binary characters

Oct (x): converting integers to 8 characters

Number type:

Python numeric literals: boolean, Integer, float, negative

True:1

false:0

is an immutable type

The math module enables advanced arithmetic operations

Sequence Type:

Character type

string literal: Enclose the text in single, double, or triple quotation marks: consistent before and after

If you want to use Unicode encoding, use the character u to identify before the character, such as U "mageedu"

Document string: The first statement of a module, class, or function is a character, and the string becomes a document string that can be referenced by using __doc__

Operator:

Index operator: [i] can use a negative number, that is, the value is inverted

Slice operator: [I:J]

Extended slices: [I:j:stride]

Support operations

Index, Slice, min (), Max (), Len (), etc.

Support operations

Object-owned operations

List:

Container type

An ordered set of arbitrary objects that access elements through an index, mutable objects

Heterogeneous, arbitrary nesting

Support in situ modification:

Modifies the specified index element, modifies the specified shard, deletes the statement, and the built-in method

L1 + L2: Merges two lists, returns a new list, does not modify the original list

L1 * N: Repeats L1 n times, returns a new list

In: Member relationship Judge character, usage obj in container

Not in:obj not in container

List parsing: []

List replication methods:

l1=[1,2,3,4]

Shallow copy

L2=l1

Deep copy

Import Copy

L2=copy.deepcopy (L1)

l2=l1[:]

Meta-group:

Expression symbol: ()

Container type

An ordered collection of arbitrary objects, which are accessed through an index, immutable objects, fixed lengths

Supports heterogeneous, nested

Common operations:

()

(1,)

(from)

T1 + T2

T1 * N

In

Not in:

Although the tuple itself is immutable, modifications to such elements do not return tuples if they are nested inside a mutable type element

Dictionary: Dict

Dictionaries are also referred to as associative arrays or hash lists in other programming languages

element access by key, unordered set, mutable type container, variable length, heterogeneous, nested

{Key1:value1,key2:value2,....}

{}: Empty dictionary

Dictionary copy: D2=d1.copy ()

D1.iteritems: Returns an iterator object Python QuickStart (02) _

Python Quick Start 02-0529