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This article will explain in detail the basic knowledge about python. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

I. operator

In

"hello" in "asdfashellosdfadfadfa"

"li" in ['li','ok']

II. Basic data types

Int

A. Creation method

N1 = 123 # based on the int class, an object is created

N2 = int123 # created an object based on the int class

The unique features are:

Int class

Function 1

Function 1

Function 1

...

_ _ init__ initialization

B. Int internal optimization

N1 = 123

N2 = N1

N1 = 123

N2 = 123

= two copies of memory =

-5000257 this can be changed by modifying the source code, evolved from the c language, look up the source code

N1 = 123

N2 = 123

N1 = 123

N2 = 123

= = "memory address of the object = id (object or variable name of the object) so that you can view the memory address

C, length limit

With int, it is out of range (defined according to the computer)

32-bit operating system-2x 31-2m 31-1

64-bit operating system-2, 3, 3, 6, 3, 3, 6, 3, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 2, 6, 6, 6, 2, 6, 6, 6, 2, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 2, 6, 4, 6, 6, 6, 6, 6, 6, 6, 4, 6, 4, 6, 4, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 4, 6, 4, 6, 4, 6, 6,

Long

Bytes: you can convert characters to bytes

Str

A. Creation method

S1 = "zq"

S1 = str ("zq")

B, unique functions

# remove spaces at both ends

# s1.strip ()

# to. The beginning

# s1.startwith ()

# finding subsequence

# s1.find ()

# replace a subsequence in a string with the specified value

# s1.replace ()

# change uppercase

# s1.upper ()

# Yes. Is it?

# s1.isalpha ()

C. Public function

Index: only one element can be fetched

Slices: taking multiple elements

Len:

For:

Coding, for:

Name = "Li Lu"

For i in name:

Print (I)

Bytes_list = bytes (I, encoding='utf-8')

Print (bytes_list)

For b in bytes_list:

# bytes default to hexadecimal

# output default hexadecimal per byte

Print (bbin (b))

1. When the for loop is in version 3.6, each element of the loop is a "character"

2. Character = "byte

Bytes_list = bytes ("string", encoding='utf-8')

# utf-8-"3 bytes

# gbk-"2 bytes

Print (bytes_list) # defaults to hexadecimal for every byte

For b in bytes_list:

Print (b) # defaults to decimal for each byte

The number in base 3 and 10 = "base 2"

Len

Id

Bin (decimal number)

Conversion of d, bytes and str

A = "Zhang Qiang"

# convert strings to bytes

B1 = bytes (a, encoding='utf-8')

Print (b1)

B2 = bytes (a _

Print (b2)

# convert bytes to strings

Print (str (b1 recording encodingbirds utfmur8')

Print (str (b2)

#

X = str ()

# create a string

# convert to string

O = bytes ()

# create bytes

# convert to bytes, strings, what encoding type of bytes to program

Str ()

Str class _ _ init__

List

A, create and transform

1. Create

A "collection" of variable elements, a list

Li = [11, 22, 33, 44]

Li = list ()

-

Str-> create strings, or convert others to strings

List-> create lists and convert other elements into lists

Li = ([11, 22, 33, 44])

2. Conversion

# iterable iterable: for can be cycled

A1 = "Zhang Qiang"

# for, character = > iterable

Li = list (A1) # for loop, which treats each element of the loop as an element of the list

Print (li)

# Dictionary #

Dic = {"K1": "zq", "K2": "sdfsdf"} # Note are curly braces

L3 = list (dic)

Print (L3)

L4 = list (dic.values ())

Print (L4)

L5 = list (dic.items ())

Print (L5)

# string, tuple, dictionary = "list

B, list-specific features

Li = [11, 22, 22, 3]

# append

# li.append ()

# clear

# li.clear ()

# extend yourself to yourself with another iterable object

# str string, list list, dictionary dic, tuple tuple

# z = "Zhang Qiang"

# li.extend (z)

# print (li)

# Flip, flip your own internal elements

# li.reverse ()

# insert the specified element into the specified location

# li.insert (1)

# print (li)

C. Public function

Li = ["zq", "fd", "gg", "rg"]

Index: only one element can be fetched

Slices: taking multiple elements

Li = ["sdf", "sdfe", "hdf", "sdgx"]

Print (li [1])

Print (li [1:3])

Sdfe # Index

['sdfe',' hdf'] # what type of slice is originally, what type of slice is taken out

For

Len

D, multi-layer nesting

Li = ['sdf','dff','we','gr']

Li = ["zq", 12, {"K1": "b1", "b2": {"qq": (11pime 22phi33), "ii": 741}}]

Li [2]-- > {"K1": "b1", "b2": {"qq": (11, 22), "ii": 741}}

Li [2] ['k2'] = > {"qq": (11 Magne22, 33), "ii": 741}

Li [2] ['k2'] ["qq"]-- > {11pr 22 pm 33}

Tuple tuple

A, create and transform

T = (11, 22, 22, 33)

T = tuple ((11, 22, 33))

T = tuple {[]} # string, list, dictionary

B. unique methods

Count index

C, nesting (elements cannot be modified)

T = (11, 22, 22, 33)

T = (112.22, ["zq", {"zq1": "Z1"}])

T [2] = ["zq", {"zq1": "Z1"}]

T [2] [1] = {"zq1": "Z1"}

T [2] [1] ["zq1"]

E, the properties of tuples can not be modified, who can not be modified-the elements of tuples cannot be modified, and the elements of elements can be modified.

# add new elements to the elements in the dictionary, two ways

Dic = {"zq1": "zz"}

# dic.update ({"zq2": 15}) # pay attention to enlarge parentheses for newly added elements

# print (dic)

Dic ["zq2"] = 15

Print (dic)

# t = (11, 22, 22, 33)

T = (112.22, ["zq", {"zq1": "Z1"}])

# print (t [2])

# print (t [2] [1])

# print (t [2] [1] ["zq1"])

# print (t)

# t [2] .append ("zz")

# print (t)

T = (112.22, ["zq", {"zq1": "Z1"}])

T [2] [1] ["zq2"] = 15

Print (t)

T [2] [1] .update ({"zq3": 15})

Print (t)

# when does it change itself? when does it produce a new one?

# General operations on strings

General string, perform a function, generate a new content, the original content remains unchanged

List, tuple, dic, perform a function and change itself

Dictionary:

1. Create

A = {"Z1": 8}

A = dict ()

Li = [11, 22, 22, 33]

# new_dict = dict (li) # this is not allowed

# new_dict = dict (enumerate (li,10))

New_dict = dict (enumerate (li,1))

Print (new_dict)

# if you want to convert the list, you can only use enumerate

two。 The internal functions of dictionaries

Dic = {"K1": 123,456, "K3": 566}

# method, no @ staticmothod, object. Method

# dic.get ()

# K1 and K2. Default is 123.

# method, with @ staticmothod, class. Method

# n = dic.fromkeys (['K1BQ / K2MJ / K3'], "123")

The function of # fromkeys is to find the key value that exists in the dictionary and reassign it.

# n = dict.fromkeys (['K1BQ / K2MJ / K3'], "123")

# print (n)

N = dict.fromkeys (['K1BZ, K2MJ, K3'], [])

Print (n)

N ['K1'] .append (' x')

Print (n)

This is the end of this article on "basic knowledge points of python". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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