超常用的Python代码片段 | 备忘单

Python Strings

• strip
• lstrip
• rstrip
• upper
• isupper
• lower
• islower
• in
• not in
• ord
• Template Strings
• Pyperclip module

strip()

>>> check = '    Python is great!     '  # removes characters from both left and right based on the argument
>>> check.strip()
'Python is great'

lstrip()

>>> check.lstrip()
'Python is great!     ' ## removes characters from left based on the argument

rstrip()

>>> check.rstrip() ## removes characters from left based on the argument
'     Python is great!'

ord()

    >>> ord('A'), ord('Z')
    (65, 90)
    >>> ord('0'), ord('9')
    (48, 57)
    >>> ord('a'), ord('z')
    (97, 122)
    >>> ord('B'), ord('Y')
    (66, 89)

The in and not in Operators with string

    >>> 'Python' in 'Python is great!'
    True
    >>> 'python' in 'Python'
    False
    >>> 'PYTHON' in 'Python is great!'
    False
    >>> '' in 'python'
    True
    >>> 'Python' not in 'python and javascript' ## Matches case
    True

The in and not in Operators with list

    >>> a = ['P', 'y', 't', 'h', 'o', 'n']
    >>> 'p' in a
    False
    >>> 'P' in a
    True
    >>> 'o' in a
    True
    
    ## On Integers List
    >>> a = [1, 2, 3, 5]
    >>> 5 in a
    True
    >>> 4 in a
    False
    >>> 1 in a
    True

The upper(), lower(), isupper(), islower() string methods

    >>> check = 'Hello world!'
    >>> check = check.lower() ## converts check to lower
    >>> check
    'hello world!'
    >>> check = check.isupper() ## checks whether check variable is upper or not. 
    False
    >>> check = check.islower() ## checks whether check variable is upper or not. 
    True
    >>> check = check.upper() ## converts check to upper
    >>> check
    'HELLO WORLD!'
    >>> check = check.isupper() ## checks whether check variable is upper or not. 
    True
    >>> check = check.islower() ## checks whether check variable is upper or not. 
    False

Template Strings

模板字符串是一种更简单的机制，用于处理用户生成的格式字符串

    >>> from string import Template
    >>> language = 'Python'
    >>> t = Template('$name is great!')
    >>> t.substitute(name=language) ## Substitutes name with language variable
    'Python is great!'

Pyperclip

Pyperclip是一个Python库，可以帮助我们轻松复制和粘贴字符串
首先使用pip安装

    pip install pyperclip

    >>> import pyperclip
    >>> pyperclip.copy('Hello World') ## Copy Hello World
    >>> pyperclip.paste()
    'Hello World'

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Numbers

Python中有三种数字类型

• int (e.g. 2, 4, 20)
  • bool (e.g. False and True, acting like 0 and 1)
• float (e.g. 5.0, 1.6)
• complex (e.g. 5+6j, 4-3j)

Basic Functions

    a = pow(2, 3) ## Or: 2 ** 3
    b = abs(5) ##  = abs()

Constants

    from math import e, pi

Trigonometry

    from math import cos, acos, sin, asin, tan, atan, degrees, radians

Logarithm

    from math import log, log10, log2
    <float> = log(<real> [, base])  # Base e, if not specified.

Infinity, nan

    from math import inf, nan, isinf, isnan

Or:

    float('inf'), float('nan')

Statistics

    from statistics import mean, median, variance, pvariance, pstdev

Random

    from random import random, randint, choice, shuffle
    <float> = random()
    <int>   = randint(from_inclusive, to_inclusive)
    <el>    = choice(<list>)
    shuffle(<list>)

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Combinatorics

每个函数都返回一个迭代器。
如果要打印迭代器，需要将其传递给list（）函数

    from itertools import product, combinations, combinations_with_replacement, permutations

    >>> product([0, 1], repeat=3)
    [(0, 0, 0), (0, 0, 1), (0, 1, 0), (0, 1, 1), 
     (1, 0, 0), (1, 0, 1), (1, 1, 0), (1, 1, 1)]
    
    >>> product('ab', '12')
    [('a', '1'), ('a', '2'),
     ('b', '1'), ('b', '2')]
    
    >>> combinations('abc', 2)
    [('a', 'b'), ('a', 'c'), ('b', 'c')]
    
    >>> combinations_with_replacement('abc', 2)
    [('a', 'a'), ('a', 'b'), ('a', 'c'), 
     ('b', 'b'), ('b', 'c'), 
     ('c', 'c')]
    
    >>> permutations('abc', 2)
    [('a', 'b'), ('a', 'c'), 
     ('b', 'a'), ('b', 'c'), 
     ('c', 'a'), ('c', 'b')]

    def test_integer_numbers():
        """Integer type
        Int, or integer, is a whole number, positive or negative,
        without decimals, of unlimited length.
        """
    
        positive_integer = 1
        negative_integer = -3255522
        big_integer = 35656222554887711
    
        assert isinstance(positive_integer, int)
        assert isinstance(negative_integer, int)
        assert isinstance(big_integer, int)
    
    
    def test_booleans():
        """Boolean
        Booleans represent the truth values False and True. The two objects representing the values
        False and True are the only Boolean objects. The Boolean type is a subtype of the integer type,
        and Boolean values behave like the values 0 and 1, respectively, in almost all contexts, the
        exception being that when converted to a string, the strings "False" or "True" are returned,
        respectively.
        """
    
        true_boolean = True
        false_boolean = False
    
        assert true_boolean
        assert not false_boolean
    
        assert isinstance(true_boolean, bool)
        assert isinstance(false_boolean, bool)
    
        # Let's try to cast boolean to string.
        assert str(true_boolean) == "True"
        assert str(false_boolean) == "False"
    
    
    def test_float_numbers():
        """Float type
        Float, or "floating point number" is a number, positive or negative,
        containing one or more decimals.
        """
    
        float_number = 7.0
        # Another way of declaring float is using float() function.
        float_number_via_function = float(7)
        float_negative = -35.59
    
        assert float_number == float_number_via_function
        assert isinstance(float_number, float)
        assert isinstance(float_number_via_function, float)
        assert isinstance(float_negative, float)
    
        # Float can also be scientific numbers with an "e" to indicate
        # the power of 10.
        float_with_small_e = 35e3
        float_with_big_e = 12E4
    
        assert float_with_small_e == 35000
        assert float_with_big_e == 120000
        assert isinstance(12E4, float)
        assert isinstance(-87.7e100, float)
    
    
    def test_complex_numbers():
        """Complex Type"""
    
        complex_number_1 = 5 + 6j
        complex_number_2 = 3 - 2j
    
        assert isinstance(complex_number_1, complex)
        assert isinstance(complex_number_2, complex)
        assert complex_number_1 * complex_number_2 == 27 + 8j
    
    
    def test_number_operators():
        """Basic operations"""
    
        # Addition.
        assert 2 + 4 == 6
    
        # Multiplication.
        assert 2 * 4 == 8
    
        # Division always returns a floating point number.
        assert 12 / 3 == 4.0
        assert 12 / 5 == 2.4
        assert 17 / 3 == 5.666666666666667
    
        # Modulo operator returns the remainder of the division.
        assert 12 % 3 == 0
        assert 13 % 3 == 1
    
        # Floor division discards the fractional part.
        assert 17 // 3 == 5
    
        # Raising the number to specific power.
        assert 5 ** 2 == 25  # 5 squared
        assert 2 ** 7 == 128  # 2 to the power of 7
    
        # There is full support for floating point; operators with
        # mixed type operands convert the integer operand to floating point.
        assert 4 * 3.75 - 1 == 14.0

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File

• Read File
• Write a File
• Copy File
• Move File
• Readline

Read a file

在Python 3中，如果文件未以二进制模式打开，则编码将由locale.getpreferredencoding（False）或用户输入确定。

    >>> with open("/etc/hosts", encoding="utf-8") as f:
    ...     content = f.read()
    ...
    >>> print(type(content))
    <class 'str'>

In python3 binary mode

    >>> with open("/etc/hosts", "rb") as f:
    ...     content = f.read()
    ...
    >>> print(type(content))
    <class 'bytes'>

In python2

    ## The content of the file is a byte string, not a Unicode string.
    >>> with open("/etc/passwd") as f:
    ...    content = f.read()
    >>> print(type(content))
    <type 'str'>
    >>> print(type(content.decode("utf-8")))
    <type 'unicode'>

Write a File

    >>> file_content = "Python is great!"
    >>> with open("check.txt", "w") as file:
    ...     file.write(file_content)

Copy a file

    >>> from distutils.file_util import copy_file
    >>> copy_file("a", "b")
    ('b', 1)

Move a File

    >>> from distutils.file_util import move_file
    >>> move_file("./a", "./b")
    './b'

Readline

    ## If you are not using linux machine try to change the file path to read
    >>> with open("/etc/hosts") as f:
    ...     for line in f:
    ...         print(line, end='')
    ...
    127.0.0.1       localhost
    255.255.255.255     broadcasthost
    ::1             localhost

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Python Functions

• Lambda
• Declare Function
• Document Function
• Get Function Name
• Arguments
• Decorator
• Generator

Lambda

    >>> fn = lambda x: x**3
    >>> fn(2)
    8
    
    >>> (lambda x: x**3)(2)
    8
    
    >>> (lambda x: [x * _ for _ in range(10)])(3)
    [0, 3, 6, 9, 12, 15, 18, 21, 24, 27]

Declare Function

    def fn_name(): ## Where fn_name represents the function name
        ........
        ........

Get Function Name

    ## First Declare a function 
    def fn_name():
        .......
        .......
    
    
    >>> fn_name.__name__
    'fn_name'

Document a Function

    ## Document a function with three single quotes
    def check():
        '''This function is documented'''
        return
    
    
    >>> check.__doc__
    'This function is documented'

Arguments

    >>> def multiply(a, b=0): ## b is 0 by default
    ...     return a * b
    ...
    >>> multiply(1, 3) ## 3 * 1
    3
    >>> multiply(5) ## 5 * 0
    0
    >>> multiply(5, b=3) ## 5 * 3
    15

Generator

    def count(start, step):
        while True:
            yield start
            start += step
    
    >>> counter = count(10, 5)
    >>> next(counter)
    (15)
    
    >>> next(counter) ## Increments by 5 from the previous result
    (20)
    
    >>> next(counter)
    (25)
    
    >>> next(counter), next(counter), next(counter)
    (30, 35, 40)

Decorator

    >>> from functools import wraps
    
    >>> def decorator_func(func):
    ...     @wraps(func)
    ...     def wrapper(*args, **kwargs):
    ...         print("Before calling {}.".format(func.__name__))
    ...         ret = func(*args, **kwargs)
    ...         print("After calling {}.".format(func.__name__))
    ...         return ret
    ...     return wrapper
    ...
    >>> @decorator_func
    ... def check():
    ...     print("Inside check function.")
    ...
    >>> check()
    Before calling check.
    Inside check function.
    After calling check.

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Classes

• Definition
• Class Objects
• Instance Objects
• Method Objects
• Inheritance
• Multiple Inheritance

Class Definition

Python是一种面向对象的编程语言。 Python中的几乎所有东西都是一个对象，具有其属性和方法。 Class类似于对象构造函数，或者是用于创建对象的“蓝图”。

    def test_class():
        """Class definition."""
    
        # Class definitions, like function definitions (def statements) must be executed before they
        # have any effect. (You could conceivably place a class definition in a branch of an if
        # statement, or inside a function.)
    
        class GreetingClass:
            """Example of the class definition
            This class contains two public methods and doesn't contain constructor.
            """
            name = 'Bisrat'
    
            def say_hello(self):
                """Class method."""
                # The self parameter is a reference to the class itself, and is used to access variables
                # that belongs to the class. It does not have to be named self , you can call it
                # whatever you like, but it has to be the first parameter of any function in the class.
                return 'Hello ' + self.name
    
            def say_goodbye(self):
                """Class method."""
                return 'Goodbye ' + self.name
    
        # When a class definition is entered, a new namespace is created, and used as the local scope —
        # thus, all assignments to local variables go into this new namespace. In particular, function
        # definitions bind the name of the new function here.
    
        # Class instantiation uses function notation. Just pretend that the class object is a
        # parameterless function that returns a new instance of the class. For example the following
        # code will creates a new instance of the class and assigns this object to the local variable.
        greeter = GreetingClass()
    
        assert greeter.say_hello() == 'Hello Bisrat'
        assert greeter.say_goodbye() == 'Goodbye Bisrat'
    
    >>> print(type(content))
    <class 'str'>

Class Objects

    def test_class_objects():
        """Class Objects.
        Class objects support two kinds of operations:
        - attribute references
        - instantiation.
        """
    
        # ATTRIBUTE REFERENCES use the standard syntax used for all attribute references in
        # Python: obj.name. Valid attribute names are all the names that were in the class’s namespace
        # when the class object was created. For class MyCounter the following references are valid
        # attribute references:
    
        class ComplexNumber:
            """Example of the complex numbers class"""
    
            real = 0
            imaginary = 0
    
            def get_real(self):
                """Return real part of complex number."""
                return self.real
    
            def get_imaginary(self):
                """Return imaginary part of complex number."""
                return self.imaginary
    
        assert ComplexNumber.real == 0
    
        # __doc__ is also a valid attribute, returning the docstring belonging to the class
        assert ComplexNumber.__doc__ == 'Example of the complex numbers class'
    
        # Class attributes can also be assigned to, so you can change the value of
        # ComplexNumber.counter by assignment.
        ComplexNumber.real = 10
        assert ComplexNumber.real == 10
    
        # CLASS INSTANTIATION uses function notation. Just pretend that the class object is a
        # parameterless function that returns a new instance of the class. For example
        # (assuming the above class):
        complex_number = ComplexNumber()
    
        assert complex_number.real == 10
        assert complex_number.get_real() == 10
    
        # Let's change counter default value back.
        ComplexNumber.real = 10
        assert ComplexNumber.real == 10
    
        # The instantiation operation (“calling” a class object) creates an empty object. Many classes
        # like to create objects with instances customized to a specific initial state. Therefore a
        # class may define a special method named __init__(), like this:
    
        class ComplexNumberWithConstructor:
            """Example of the class with constructor"""
            def __init__(self, real_part, imaginary_part):
                self.real = real_part
                self.imaginary = imaginary_part
    
            def get_real(self):
                """Return real part of complex number."""
                return self.real
    
            def get_imaginary(self):
                """Return imaginary part of complex number."""
                return self.imaginary
    
        complex_number = ComplexNumberWithConstructor(3.0, -4.5)
        assert complex_number.real, complex_number.imaginary == (3.0, -4.5)

Instance Object

    def test_instance_objects():
        # DATA ATTRIBUTES need not be declared; like local variables, they spring into existence when
        # they are first assigned to. For example, if x is the instance of MyCounter created above,
        # the following piece of code will print the value 16, without leaving a trace.
    
        # pylint: disable=too-few-public-methods
        class DummyClass:
            pass
    
        dummy_instance = DummyClass()
    
        # pylint: disable=attribute-defined-outside-init
        dummy_instance.temporary_attribute = 1
        assert dummy_instance.temporary_attribute == 1
        del dummy_instance.temporary_attribute

Method Objects

    class MyCounter:
        """A simple example of the counter class"""
        counter = 10
    
        def get_counter(self):
            """Return the counter"""
            return self.counter
    
        def increment_counter(self):
            """Increment the counter"""
            self.counter += 1
            return self.counter
    
    
    def test_method_objects():
        """Method Objects."""
    
      
        # object types can have methods as well. For example, list objects have methods called append,
        
        counter = MyCounter()
        assert counter.get_counter() == 10
    
        get_counter = counter.get_counter
        assert get_counter() == 10
    
      
    
        assert counter.get_counter() == 10
        assert MyCounter.get_counter(counter) == 10

Inheritance

    # pylint: disable=too-few-public-methods
    class Person:
        """Example of the base class"""
        def __init__(self, name):
            self.name = name
    
        def get_name(self):
            """Get person name"""
            return self.name
    
    
    # The syntax for a derived class definition looks like this.
    class Employee(Person):
        
        def __init__(self, name, staff_id):
            Person.__init__(self, name)
            # You may also use super() here in order to avoid explicit using of parent class name:
            # >>> super().__init__(name)
            self.staff_id = staff_id
    
        def get_full_id(self):
            """Get full employee id"""
            return self.get_name() + ', ' + self.staff_id
    
    
    def test_inheritance():
        """Inheritance."""
    
        # There’s nothing special about instantiation of derived classes: DerivedClassName() creates a
        # new instance of the class. Method references are resolved as follows: the corresponding class
        # attribute is searched, descending down the chain of base classes if necessary, and the method
        # reference is valid if this yields a function object.
        person = Person('Bisrat')
        employee = Employee('John', 'A23')
    
        assert person.get_name() == 'Bisrat'
        assert employee.get_name() == 'John'
        assert employee.get_full_id() == 'John, A23'
    
        # Python has two built-in functions that work with inheritance:
        #
        # - Use isinstance() to check an instance’s type: isinstance(obj, int) will be True only if
        # obj.__class__ is int or some class derived from int.
        #
        # - Use issubclass() to check class inheritance: issubclass(bool, int) is True since bool is
        # a subclass of int. However, issubclass(float, int) is False since float is not a subclass
        # of int.
    
        assert isinstance(employee, Employee)
        assert not isinstance(person, Employee)
    
        assert isinstance(person, Person)
        assert isinstance(employee, Person)
    
        assert issubclass(Employee, Person)
        assert not issubclass(Person, Employee)

Multiple Inheritance

    def test_multiple_inheritance():
        """Multiple Inheritance"""
        class Clock:
            """Clock class"""
    
            time = '10:17 PM'
    
            def get_time(self):
                """Get current time
                Method is hardcoded just for multiple inheritance illustration.
                """
                return self.time
    
       
        class Calendar:
            """Calendar class"""
    
            date = '12/08/2018'
    
            def get_date(self):
                """Get current date
                Method is hardcoded just for multiple inheritance illustration.
                """
                return self.date
    
        # Python supports a form of multiple inheritance as well. A class definition with multiple
        # base classes looks like this.
        class CalendarClock(Clock, Calendar):
           
        calendar_clock = CalendarClock()
    
        assert calendar_clock.get_date() == '12/08/2018'
        assert calendar_clock.get_time() == '11:23 PM'

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Date and Time

• DateTime
• Time Delta
• Calendar

datetime

    from datetime import date 
    from datetime import time
    from datetime import datetime
    
    >>> today = date.today()
    >>> print(today)
    2019-03-04
    
    >>> print(today.day, today.month, today.year)
    (4, 3, 2019)
    
    >>> print(today.weekday()) ## returns an integers in the range 0 to 6, where 0 represents Monday and 6 represents Sunday.
    0
    
    >>> today = datetime.now()
    >>> print(today)
    2019-03-04 21:55:56.228000
    
    >>> time = datetime.time(datetime.now())
    >>> print(time) 
    21:56:16.040000

Time Delta

This module is used to perform date and time calculations.

    from datetime import date 
    from datetime import time
    from datetime import datetime
    from datetime import timedelta
    
    print(timedelta(days=365, hours=5, minutes=1)) # 365 days, 5:01:00
    today  = datetime.now()
    print(today + timedelta(days=60)) # 2019-03-29 18:41:46.720811
    print(today - timedelta(days=57)) # 2018-12-02 18:42:36.774421

timedelta对象采用以下参数：天，秒，微秒，毫秒，分钟，小时，周。 要查找过去或将来的日期，只需使用带有当前日期所需差异的加号或减号。

Calendar

日历相关操作并以格式化方式显示

    import calendar
    
    c = calendar.TextCalendar(calendar.MONDAY)
    st = c.formatmonth(2017, 1, 0,0)
    print(st)
    
    hc = calendar.HTMLCalendar(calendar.MONDAY)
    st = hc.formatmonth(2017, 1)
    print(st)
    
    #Output
    '''
        January 2017
    Mo Tu We Th Fr Sa Su
                       1
     2  3  4  5  6  7  8
     9 10 11 12 13 14 15
    16 17 18 19 20 21 22
    23 24 25 26 27 28 29
    30 31
    
    

    
January 2017
    
Mon
Tue
Wed
Thu
Fri
Sat
Sun
    
 
 
 
 
 
 
1
    
2
3
4
5
6
7
8
    
9
10
11
12
13
14
15
    
16
17
18
19
20
21
22
    
23
24
25
26
27
28
29
    
30
31
 
 
 
 
 
    
    '''

.HTMLCalendar以表格的形式返回HTML代码。Calendar.SUNDAY表示格式化日历中的第一天是星期日，在上边的例子中，使用了Calendar.MONDAY。因此，我们可以在输出中看到表示中的第一天是星期一。

Iterating through dates of a month

    import calendar
    
    c = calendar.TextCalendar(calendar.MONDAY)
    for i in c.itermonthdays(2017, 8):
        print(i, end = ' ')
    print('')
    for name in calendar.month_name:
        print(name, end = ' ')
    print('')
    for day in calendar.day_name:
        print(day, end = ' ')
    '''
    Output:
    0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 0 0 0
     January February March April May June July August September October November December
    Monday Tuesday Wednesday Thursday Friday Saturday Sunday
    '''

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Regular Expressions

非特殊字符匹配

    \       Escape special char or start a sequence.

    .       Match any char except newline, see re.DOTALL

    ^       Match start of the string, see 
    re.MULTILINE

    $       Match end of the string, see re.MULTILINE

    []      Enclose a set of matchable chars

    R|S     Match either regex R or regex S.

    ()      Create capture group, & indicate precedence
    After '[', enclose a set, the only special chars are:

    ]   End the set, if not the first char

    -   A range, eg. a-c matches a, b or c

    ^   Negate the set only if it is the 1st char

Regular Expression Examples

re.findall()

    # split all string from a sentence
    >>> import re
    >>> source = "Python is great!"
    >>> re.findall('[\w]+', source)
    ['Python', 'is', 'great!']

Match hex color value

    >>> re.match('^#?([a-f0-9]{6}|[a-f0-9]{3})$', '#ffffff')
    <_sre.SRE_Match object at 0x0000000002F04120>
    >>> re.match('^#?([a-f0-9]{6}|[a-f0-9]{3})$', '#cdcdcd')
    <_sre.SRE_Match object at 0x0000000002EA3160>

Match username doesn’t have any special characters

    True
    >>> re.match('^\w|[-_]{3,16}$', 'che%ck') is not None
    False

Match email address format

    re.match('^([a-z0-9_\.-]+)@([\da-z\.-]+)\.([a-z\.]{2,6})$',
    ...          '[email protected]')
    <_sre.SRE_Match object at 0x0000000002EA3180>

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Web Data Handling

• Make a Request
• Read
• Get Code
• HTML Parsing
• JSON Parsing
• XML Parsing

Make a Request

    import urllib.request ## urllib module is used to send request and receive response from a server. It can used to get html / JSON / XML data from an api.
    
    webData = request.urlopen("http://www.google.com") ## It opens a connection to google.com and returns an object of class http.client.HTTPResponse

Read

.read() return the HTML data of the webpage.

Get Code

.getcode() returns the status code of the connection establishment.

HTML Parsing

    from html.parser import HTMLParser
    
    class MyHTMLParser(HTMLParser):
        def error(self, message):
            pass
            
    parser = MyHTMLParser()
    f = open("check.html")
    if f.mode == 'r':  # file successfully opened
        contents = f.read()
        parser.feed(contents)

JSON Parsing

    import json
    json_data = json.loads(response)

XML Parsing

    import xml.dom.minidom
    doc = minidom.parse("check.xml")

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Asyncio

• Definition
• asyncio.run
• Socket with Asyncio
• Move File
• Readline

asyncio是Python 3.5中包含的一个库，采用非常非常明确的异步编程方法：只有标记为async的方法编写的代码才能以异步方式调用任何代码。

asyncio.run

Python 3.7中的新功能

    >>> import asyncio
    >>> from concurrent.futures import ThreadPoolExecutor
    
    >>> e = ThreadPoolExecutor()
    >>> async def read_file(file_):
    ...     loop = asyncio.get_event_loop()
    ...     with open(file_) as f:
    ...         return (await loop.run_in_executor(e, f.read))
    ...
    >>> ret = asyncio.run(read_file('/etc/passwd'))

Socket with Asyncio

    import asyncio
    import socket
    
    host = 'localhost'
    port = 9527
    loop = asyncio.get_event_loop()
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
    s.setblocking(False)
    s.bind((host, port))
    s.listen(10)
    
    async def handler(conn):
        while True:
            msg = await loop.sock_recv(conn, 1024)
            if not msg:
                break
            await loop.sock_sendall(conn, msg)
        conn.close()
    
    async def server():
        while True:
            conn, addr = await loop.sock_accept(s)
            loop.create_task(handler(conn))
    
    loop.create_task(server())
    loop.run_forever()
    loop.close()

    output: (bash 1)
    
    $ nc localhost 9527
    Hello
    Hello

    output: (bash 2)
    
    $ nc localhost 9527
    World
    World

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Socket

获取主机名
文件传输协议（ftp）客户端
文件传输协议（ftp）服务器

Get Hostname

    >>> import socket
    >>> socket.gethostname()
    'root@bisratyalew'
    
    >>> hostname = socket.gethostname()
    
    >>> socket.gethostbyname('localhost')
    '127.0.0.1'
    
    >>> socket.gethostbyname(hostname) ### Returns ip address
    '192.168.1.3'

FTP Client

    import socket                   # Import socket module
    
    port = 60000                    # Reserve a port for your service.
    s = socket.socket()             # Create a socket object
    host = socket.gethostname()     # Get local machine name
    s.bind((host, port))            # Bind to the port
    s.listen(5)                     # Now wait for client connection.
    
    print('Server listening....')
    
    while True:
        conn, addr = s.accept()     # Establish connection with client.
        print('Got connection from', addr)
        data = conn.recv(1024)
        print('Server received', repr(data))
    
        filename = 'mytext.txt'
        with open(filename, 'rb') as f:
            in_data = f.read(1024)
            while in_data:
                conn.send(in_data)
                print('Sent ', repr(in_data))
                in_data = f.read(1024)
    
        print('Done sending')
        conn.send('Thank you for connecting')
        conn.close()
    
    
    # client side server
    
    import socket                   # Import socket module
    
    s = socket.socket()             # Create a socket object
    host = socket.gethostname()     # Get local machine name
    port = 60000                    # Reserve a port for your service.
    
    s.connect((host, port))
    s.send("Hello server!")
    
    with open('received_file', 'wb') as f:
        print('file opened')
        while True:
            print('receiving data...')
            data = s.recv(1024)
            print('data=%s', (data))
            if not data:
                break
            # write data to a file
            f.write(data)
    
    f.close()
    print('Successfully get the file')
    s.close()
    print('connection closed')

FTP Server

    """
    	File transfer protocol used to send and receive files using FTP server.
    	Use credentials to provide access to the FTP client	
    """
    
    from ftplib import FTP
    ftp = FTP('xxx.xxx.x.x')  # Enter the ip address or the domain name here
    ftp.login(user='username', passwd='password')
    ftp.cwd('/Enter the directory here/')
    
    """
    	The file which will be received via the FTP server
    	Enter the location of the file where the file is received
    """
    
    def recieve_file():
    	file_name = 'example.txt'   """ Enter the location of the file """
    	with open(file_name, 'wb') as LocalFile:
    		ftp.retrbinary('RETR ' + file_name, LocalFile.write, 1024)
    	ftp.quit()
    
    """
    	The file which will be sent via the FTP server
    	The file send will be send to the current working directory
    """
    
    def send_file():
    	file_name = 'example.txt'   """ Enter the name of the file """
    	with open(file_name, 'rb') as LocalFile:
    		ftp.storbinary('STOR ' + file_name, LocalFile)
    	ftp.quit()

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