poem = '''\
Programming is fun
When the work is done
if you wanna make your work also fun:
    use Python!
'''

# 打开文件以编辑（writing）
f = open('poem.txt', 'w')
# 向文件中编写文本
f.write(poem)
# 关闭文件
f.close()

# 如果没有特别指定，将假定启用默认的阅读（read）模式
f = open('poem.txt')
while True:
    line = f.readline()
    # 零长度指示 EOF
    if len(line) == 0:
        break
    # 每行的末尾都已经有了换行符，因为它是从一个文件中进行读取的
    print(line, end='')
    
# 关闭文件
f.close()

输出：
$ python3 io_using_file.py
Programming is fun
When the work is done
if you wanna make your work also fun:
    use Python!

# encoding=utf-8
import time

def main():
    # 一次性读取整个文件内容
    with open('致橡树.txt', 'r', encoding='utf-8') as f:
        print(f.read())

    # 通过for-in循环逐行读取
    with open('致橡树.txt', mode='r') as f:
        for line in f:
            print(line, end='')
            time.sleep(0.5)
    print()

    # 读取文件按行读取到列表中
    with open('致橡树.txt') as f:
        lines = f.readlines()
    print(lines)

if __name__ == '__main__':
    main()

def main():
    try:
        with open('python.jpg', 'rb') as fs1:
            data = fs1.read()
            print(type(data))  # <class 'bytes'>
        with open('python_bak.jpg', 'wb') as fs2:
            fs2.write(data)
    except FileNotFoundError as e:
        print('指定的文件无法打开.')
    except IOError as e:
        print('读写文件时出现错误.')
    print('程序执行结束.')

if __name__ == '__main__':
    main()

import json

def main():
    mydict = {
        'name': '狄仁杰',
        'age': 38,
        'qq': 957658,
        'friends': ['王大锤', '李元芳'],
        'cars': [
            {'brand': 'BYD', 'max_speed': 180},
            {'brand': 'Audi', 'max_speed': 280},
            {'brand': 'Benz', 'max_speed': 320}
        ]
    }
    try:
        with open('data.json', 'w', encoding='utf-8') as fs:
            json.dump(mydict, fs)
    except IOError as e:
        print(e)
    print('保存数据完成!')

if __name__ == '__main__':
    main()

import pickle

# 我们存储相关对象的文件的名称
shoplistfile = 'shoplist.data'

# 需要购买的物品清单
shoplist = ['apple', 'mango', 'carrot']

# 准备写入文件
f = open(shoplistfile, 'wb')

# 转储对象至文件
pickle.dump(shoplist, f)
f.close()

# 清除 shoplist 变量
del shoplist

# 重新打开存储文件
f = open(shoplistfile, 'rb')

# 从文件中载入对象
storedlist = pickle.load(f)
print(storedlist)

输出：
$ python io_pickle.py
['apple', 'mango', 'carrot']

app = create_app(name, options)


# =====================================
# 请勿在此处添加 get post等app路由行为 !!!
# =====================================


if __name__ == '__main__':
    app.run()
    
    
#  不推荐的写法(不要写函数原型等废话)
def function(a, b):
    """function(a, b) -> list"""
    ... ...


#  正确的写法
def function(a, b):
    """计算并返回a到b范围内数据的平均值"""
    ... ...

# 模块命名
import decoder
import html_parser


# 类命名
class Farm():
    pass

class AnimalFarm(Farm):
    pass

  
# 私有类命名
class _PrivateFarm(Farm):
    pass

  
# 函数命名
def run():
    pass

def run_with_env():
    pass
 

# 私有函数命名
class Person():

    def _private_func():
        pass
      
      
# 变量命名
if __name__ == '__main__':
    count = 0
    school_name = ''
    

# 常量命名
MAX_CLIENT = 100
MAX_CONNECTION = 1000
CONNECTION_TIMEOUT = 600

import unittest

from mydict import Dict

class TestDict(unittest.TestCase):

    def test_init(self):
        d = Dict(a=1, b='test')
        self.assertEqual(d.a, 1)
        self.assertEqual(d.b, 'test')
        self.assertTrue(isinstance(d, dict))

    def test_key(self):
        d = Dict()
        d['key'] = 'value'
        self.assertEqual(d.key, 'value')

    def test_attr(self):
        d = Dict()
        d.key = 'value'
        self.assertTrue('key' in d)
        self.assertEqual(d['key'], 'value')
        
    def test_keyerror(self):
        d = Dict()
        with self.assertRaises(KeyError):
            value = d['empty']

    def test_attrerror(self):
        d = Dict()
        with self.assertRaises(AttributeError):
            value = d.empty
            
if __name__ == '__main__':
    unittest.main()

import sys
import time

f = None
try:
    f = open("poem.txt")
    # 我们常用的文件阅读风格
    while True:
        line = f.readline()
        if len(line) == 0:
            break
        print(line, end='')
        sys.stdout.flush()
        print("Press ctrl+c now")
        # 为了确保它能运行一段时间
        time.sleep(2)
except IOError:
    print("Could not find file poem.txt")
except KeyboardInterrupt as ki:
    print("!! You cancelled the reading from the file.")
finally:
    if f:
        f.close()
    print("(Cleaning up: Closed the file)")
    
输出：
$ python exceptions_finally.py
Programming is fun
Press ctrl+c now
^C!! You cancelled the reading from the file.
(Cleaning up: Closed the file)

class Person:
    def __init__(self, name):
        self.name = name

    def say_hi(self):
        print('Hello, my name is', self.name)

p = Person('Swaroop')
p.say_hi()
# 前面两行同时也能写作
# Person('Swaroop').say_hi()

输出：
$ python oop_init.py
Hello, my name is Swaroop

# coding=UTF-8

class Robot:
    """表示有一个带有名字的机器人"""

    # 一个类变量，用来计数机器人的数量
    population = 0

    def __init__(self, name):
        """初始化数据"""
        
        # 一个对象变量
        self.name = name
        print("(Initializing {})".format(self.name))

        # 当有人被创建时，机器人将会增加人口数量
        Robot.population += 1

    def die(self):
        """我挂了"""
        print("{} is being destroyed!".format(self.name))

        Robot.population -= 1

        if Robot.population == 0:
            print("{} was the last one.".format(self.name))
        else:
            print("There are still {:d} robots working.".format(
                Robot.population))

    def say_hi(self):
        """来自机器人的诚挚问候：没问题，你做得到！"""
        print("Greetings, my masters call me {}.".format(self.name))
        
    # 类方法
    @classmethod  
    def how_many(cls):
        """打印出当前的人口数量"""
        print("We have {:d} robots.".format(cls.population))


droid1 = Robot("R2-D2")
droid1.say_hi()
Robot.how_many()

droid2 = Robot("C-3PO")
droid2.say_hi()
Robot.how_many()

print("\nRobots can do some work here.\n")

print("Robots have finished their work. So let's destroy them.")
droid1.die()
droid2.die()

Robot.how_many()

输出：
$ python oop_objvar.py
(Initializing R2-D2)
Greetings, my masters call me R2-D2.
We have 1 robots.
(Initializing C-3PO)
Greetings, my masters call me C-3PO.
We have 2 robots.

Robots can do some work here.

Robots have finished their work. So let's destroy them.
R2-D2 is being destroyed!
There are still 1 robots working.
C-3PO is being destroyed!
C-3PO was the last one.
We have 0 robots.

            ┌───────────────┐
            │ SchoolMember  │
            └───────────────┘
                    │
       ┌────────────┴────────────┐
       │                         │
       ▼                         ▼
┌─────────────┐           ┌─────────────┐
│   Teacher   │           │   Student   │
└─────────────┘           └─────────────┘

# coding=UTF-8

class SchoolMember:
    '''代表任何学校里的成员。'''
    def __init__(self, name, age):
        self.name = name
        self.age = age
        print('(Initialized SchoolMember: {})'.format(self.name))

    def tell(self):
        '''告诉我有关我的细节。'''
        print('Name:"{}" Age:"{}"'.format(self.name, self.age), end=" ")
  
class Teacher(SchoolMember):
    '''代表一位老师。'''
    def __init__(self, name, age, salary):
        SchoolMember.__init__(self, name, age)
        self.salary = salary
        print('(Initialized Teacher: {})'.format(self.name))

    def tell(self):
        SchoolMember.tell(self)
        print('Salary: "{:d}"'.format(self.salary))
        

class Student(SchoolMember):
    '''代表一位学生。'''
    def __init__(self, name, age, marks):
        SchoolMember.__init__(self, name, age)
        self.marks = marks
        print('(Initialized Student: {})'.format(self.name))

    def tell(self):
        SchoolMember.tell(self)
        print('Marks: "{:d}"'.format(self.marks))
        
t = Teacher('Mrs. Shrividya', 40, 30000)
s = Student('Swaroop', 25, 75)

# 打印一行空白行
print()

members = [t, s]
for member in members:
    # 对全体师生工作
    member.tell()
    
输出：
$ python oop_subclass.py
(Initialized SchoolMember: Mrs. Shrividya)
(Initialized Teacher: Mrs. Shrividya)
(Initialized SchoolMember: Swaroop)
(Initialized Student: Swaroop)

Name:"Mrs. Shrividya" Age:"40" Salary: "30000"
Name:"Swaroop" Age:"25" Marks: "75"

# module1.py
def foo():
    print('hello, world!')
   
# module2.py
def foo():
    print('goodbye, world!')
    
# test.py
import module1 as m1
import module2 as m2

m1.foo()  # 输出hello, world!
m2.foo()  # 输出goodbye, world!

if __name__ == '__main__':
    print('This program is being run by itself')
else:
    print('I am being imported from another module')
    
输出：
$ python module_using_name.py
This program is being run by itself

$ python
>>> import module_using_name
I am being imported from another module
>>>

def say_hello():
    # 该块属于这一函数
    print('hello world')
# 函数结束

say_hello()  # 调用函数
say_hello()  # 再次调用函数

输出：
$ python function1.py
hello world
hello world

def print_max(a, b):
    if a > b:
        print(a, 'is maximum')
    elif a == b:
        print(a, 'is equal to', b)
    else:
        print(b, 'is maximum')

# 直接传递字面值
print_max(3, 4)

x = 5
y = 7

# 以参数的形式传递变量
print_max(x, y)

输出：
$ python function_param.py
4 is maximum
7 is maximum

def say(message, times=1):
    print(message * times)

say('Hello')
say('World', 5)

输出：
$ python function_default.py
Hello
WorldWorldWorldWorldWorld

def func(a, b=5, c=10):
    print('a is', a, 'and b is', b, 'and c is', c)

func(3, 7)
func(25, c=24)
func(c=50, a=100)

输出：
$ python function_keyword.py
a is 3 and b is 7 and c is 10
a is 25 and b is 5 and c is 24
a is 100 and b is 5 and c is 50

def total(a=5, *numbers, **phonebook):
    print('a', a)

    # 遍历元组中的所有项目
    for single_item in numbers:
        print('single_item', single_item)

    # 遍历字典中的所有项目
    for first_part, second_part in phonebook.items():
        print(first_part,second_part)

print(total(10,1,2,3,Jack=1123,John=2231,Inge=1560))

输出：
$ python function_varargs.py
a 10
single_item 1
single_item 2
single_item 3
Inge 1560
John 2231
Jack 1123
None

x = 50

def func(x):
    print('x is', x)
    x = 2
    print('Changed local x to', x)

func(x)
print('x is still', x)

输出：
$ python function_local.py
x is 50
Changed local x to 2
x is still 50

x = 50

def func():
    global x

    print('x is', x)
    x = 2
    print('Changed global x to', x)

func()
print('Value of x is', x)

输出：
$ python function_global.py
x is 50
Changed global x to 2
Value of x is 2

number = 23
guess = int(input('Enter an integer : '))

if guess == number:
    # 新块从这里开始
    print('Congratulations, you guessed it.')
    print('(but you do not win any prizes!)')
    # 新块在这里结束
elif guess < number:
    # 另一代码块
    print('No, it is a little higher than that')
    # 你可以在此做任何你希望在该代码块内进行的事情
else:
    print('No, it is a little lower than that')
    # 你必须通过猜测一个大于（>）设置数的数字来到达这里。

print('Done')
# 这最后一句语句将在 if 语句执行完毕后执行。

输出：
$ python if.py
Enter an integer : 50
No, it is a little lower than that
Done

$ python if.py
Enter an integer : 22
No, it is a little higher than that
Done

$ python if.py
Enter an integer : 23
Congratulations, you guessed it.
(but you do not win any prizes!)
Done

number = 23
running = True

while running:
    guess = int(input('Enter an integer : '))

    if guess == number:
        print('Congratulations, you guessed it.')
        # 这将导致 while 循环中止
        running = False
    elif guess < number:
        print('No, it is a little higher than that.')
    else:
        print('No, it is a little lower than that.')
else:
    print('The while loop is over.')
    # 在这里你可以做你想做的任何事

print('Done')

输出：
$ python while.py
Enter an integer : 50
No, it is a little lower than that.
Enter an integer : 22
No, it is a little higher than that.
Enter an integer : 23
Congratulations, you guessed it.
The while loop is over.
Done

for i in range(1, 5):
    print(i)
else:
    print('The for loop is over')
    
输出：
$ python for.py
1
2
3
4
The for loop is over

while True:
    s = input('Enter something : ')
    if s == 'quit':
        break
    print('Length of the string is', len(s))
print('Done')

输出：
$ python break.py
Enter something : Programming is fun
Length of the string is 18
Enter something : When the work is done
Length of the string is 21
Enter something : if you wanna make your work also fun:
Length of the string is 37
Enter something : use Python!
Length of the string is 11
Enter something : quit
Done

while True:
    s = input('Enter something : ')
    if s == 'quit':
        break
    if len(s) < 3:
        print('Too small')
        continue
    print('Input is of sufficient length')
    # 自此处起继续进行其它任何处理
    
输出：
$ python continue.py
Enter something : a
Too small
Enter something : 12
Too small
Enter something : abc
Input is of sufficient length
Enter something : quit