x = str("s1") # x 输出结果为 's1'
y = str(2)    # y 输出结果为 '2'
z = str(3.0)  # z 输出结果为 '3.0'

num_int = 123
num_str = "456"
print("num_int 数据类型为:",type(num_int))
print("类型转换前，num_str 数据类型为:",type(num_str))
num_str = int(num_str)    # 强制转换为整型
print("类型转换后，num_str 数据类型为:",type(num_str))
num_sum = num_int + num_str
print("num_int 与 num_str 相加结果为:",num_sum)
print("sum 数据类型为:",type(num_sum))

a = 10
b = 20
list = [1, 2, 3, 4, 5 ]
if ( a in list ):
   print ("1 - 变量 a 在给定的列表中 list 中")
else:
   print ("1 - 变量 a 不在给定的列表中 list 中")
if ( b not in list ):
   print ("2 - 变量 b 不在给定的列表中 list 中")
else:
   print ("2 - 变量 b 在给定的列表中 list 中")

var1 = 'Hello World!'
var2 = "Runoob" 
print ("var1[0]: ", var1[0])
print ("var2[1:5]: ", var2[1:5])
执行结果如下：
var1[0]:  H
var2[1:5]:  unoo

var1 = 'Hello World!'
print ("已更新字符串 : ", var1[:6] + 'Runoob!')

para_str = """这是一个多行字符串的实例
多行字符串可以使用制表符
TAB ( \t )。
也可以使用换行符 [ \n ]。
"""
print (para_str)

>>> name = 'Runoob'
>>> f'Hello {name}'  # 替换变量
'Hello Runoob'
>>> f'{1+2}'         # 使用表达式
'3'

>>> w = {'name': 'Runoob', 'url': 'www.runoob.com'}
>>> f'{w["name"]}: {w["url"]}'
'Runoob: www.runoob.com'

list1 = ['Google', 'Runoob', 'Taobao']
list1.append('Baidu')
print ("更新后的列表 : ", list1)

list = ['Google', 'Runoob', 1997, 2000] 
print ("原始列表 : ", list)
del list[2]
print ("删除第三个元素 : ", list)

>>> a = ['a', 'b', 'c']
>>> n = [1, 2, 3]
>>> x = [a, n]
>>> x
[['a', 'b', 'c'], [1, 2, 3]]
>>> x[0]
['a', 'b', 'c']
>>> x[0][1]
'b'

stack = [3, 4, 5]
stack.append(6)
stack.append(7)
stack.pop()
print(stack)

tup1 = (12, 34.56)
tup2 = ('abc', 'xyz')
# 以下修改元组元素操作是非法的。
# tup1[0] = 100
# 创建一个新的元组
tup3 = tup1 + tup2
print (tup3)

tup = ('Google', 'Runoob', 1997, 2000)
del tup
print ("删除后的元组 tup : ")
print (tup)

>>> tup = ('r', 'u', 'n', 'o', 'o', 'b')
>>> tup[0] = 'g'     # 不支持修改元素
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment
>>> id(tup)     # 查看内存地址
4440687904
>>> tup = (1,2,3)
>>> id(tup)
4441088800    # 内存地址不一样了

d = {key1 : value1, key2 : value2, key3 : value3 }

# 使用大括号 {} 来创建空字典
emptyDict = {}
print(emptyDict)
print("Length:", len(emptyDict)) # 查看字典数量
print(type(emptyDict))

tinydict = {'Name': 'Runoob', 'Age': 7, 'Class': 'First'}
print ("tinydict['Name']: ", tinydict['Name'])

tinydict = {'Name': 'Runoob', 'Age': 7, 'Class': 'First'}
tinydict['Age'] = 8               # 更新 Age
tinydict['School'] = "菜鸟教程"  # 添加信息
del tinydict['Name'] # 删除键 'Name'
tinydict.clear()     # 清空字典
del tinydict         # 删除字典

tinydict = {'Name': 'Runoob', 'Age': 7, 'Name': '小菜鸟'}//后面那个会被记住

knights = {'gallahad': 'the pure', 'robin': 'the brave'}
for k, v in knights.items():
    print(k, v)

for i, v in enumerate(['tic', 'tac', 'toe']):
	print(i, v)

questions = ['name', 'quest', 'favorite color']
answers = ['lancelot', 'the holy grail', 'blue']
for q, a in zip(questions, answers):
    print('What is your {0}?  It is {1}.'.format(q, a))

basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
for f in sorted(set(basket)):
    print(f)

parame = {value01,value02,...}或者set(value)   比如：
set1 = {1, 2, 3, 4}            # 直接使用大括号创建集合
set2 = set([4, 5, 6, 7])      # 使用 set() 函数从列表创建集合

>>> basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}
>>> print(basket)                      # 这里演示的是去重功能
{'orange', 'banana', 'pear', 'apple'}
>>> print("banana" in basket)              # 快速判断元素是否在集合内
True
>>> print('crabgrass' in basket)
False

>>> # 下面展示两个集合间的运算.
...都要再加上一个print
>>> a = set('abracadabra')
>>> b = set('alacazam')
>>> a                                  
{'a', 'r', 'b', 'c', 'd'}
>>> a - b                              # 集合a中包含而集合b中不包含的元素
{'r', 'd', 'b'}
>>> a | b                              # 集合a或b中包含的所有元素
{'a', 'c', 'r', 'd', 'b', 'm', 'z', 'l'}
>>> a & b                              # 集合a和b中都包含了的元素
{'a', 'c'}
>>> a ^ b                              # 不同时包含于a和b的元素
{'r', 'd', 'b', 'm', 'z', 'l'}

thisset.update({1,3})或者 thisset.update([1,4],[5,6])

if condition_1:
    statement_block_1
elif condition_2:
    statement_block_2
else:
    statement_block_3

if 表达式1:
    语句
    if 表达式2:
        语句
    elif 表达式3:
        语句
    else:
        语句
elif 表达式4:
    语句
else:
    语句

match subject:
    case <pattern_1>:
        <action_1>
    case <pattern_2>:
        <action_2>
    case <pattern_3>:
        <action_3>
    case _:
        <action_wildcard>

while 判断条件(condition)：
    执行语句(statements)……

while <expr>:
    <statement(s)>
else:
    <additional_statement(s)>

a, b = 0, 1
while b < 10:
    print(b,  end=',')
    c = b
    b = a + b
    a = c

for <variable> in <sequence>:
    <statements>
else:
    <statements>

word = 'runoob'
for letter in word:
    print(letter)

>>>while True:
...     pass  # 等待键盘中断 (Ctrl+C)

for letter in 'Runoob': 
   if letter == 'o':
      pass
      print ('执行 pass 块')
   print ('当前字母 :', letter)
print ("Good bye!")

[表达式 for 变量 in 列表] 
[out_exp_res for out_exp in input_list]
或者 
[表达式 for 变量 in 列表 if 条件]
[out_exp_res for out_exp in input_list if condition]

names = ['Bob','Tom','alice','Jerry','Wendy','Smith']
new_names = [name.upper()for name in names if len(name)>3]
print(new_names)//过滤掉长度小于或等于3的字符串列表，并将剩下的转换成大写字母

>>> vec1 = [2, 4, 6]
>>> vec2 = [4, 3, -9]
>>> [x*y for x in vec1 for y in vec2]
[8, 6, -18, 16, 12, -36, 24, 18, -54]
>>> [x+y for x in vec1 for y in vec2]
[6, 5, -7, 8, 7, -5, 10, 9, -3]
>>> [vec1[i]*vec2[i] for i in range(len(vec1))]
[8, 12, -54]

{ key_expr: value_expr for value in collection }
或
{ key_expr: value_expr for value in collection if condition }

dict = {x: x**2 for x in (2,4,6)}//三个数字的平方
print(dict)

{ expression for item in Sequence }
或
{ expression for item in Sequence if conditional }

a = {x for x in 'abkxjbaugxidyskn' if x not in 'abcd'}
print(a)
print(type(a))

(expression for item in Sequence )
或
(expression for item in Sequence if conditional )

>>> a = (x for x in range(1,10))
>>> a
<generator object <genexpr> at 0x7faf6ee20a50>  # 返回的是生成器对象
>>> tuple(a)       # 使用 tuple() 函数，可以直接将生成器对象转换成元组
(1, 2, 3, 4, 5, 6, 7, 8, 9)

list=[1,2,3,4]
it = iter(list)    # 创建迭代器对象
print (next(it))   # 输出迭代器的下一个元素
print (next(it))

class MyNumbers:
  def __iter__(self):
    self.a = 1
    return self//返回 self，即当前对象本身。这意味着 MyNumbers 类的实例是一个迭代器对象
 
  def __next__(self):
    x = self.a
    self.a += 1
    return x
 
myclass = MyNumbers()
myiter = iter(myclass)//使用内置函数 iter() 将 myclass 实例转换为一个迭代器对象，并将其赋值给变量 myiter。通过调用 iter() 函数，会自动调用对象的 __iter__() 方法，因此 myclass 实例将成为一个迭代器对象
 
print(next(myiter))
print(next(myiter))
print(next(myiter))
print(next(myiter))
print(next(myiter))

class MyNumbers:
  def __iter__(self):
    self.a = 1
    return self
 
  def __next__(self):
    if self.a <= 20:
      x = self.a
      self.a += 1
      return x
    else:
      raise StopIteration
 
myclass = MyNumbers()
myiter = iter(myclass)
 
for x in myiter:
  print(x)

def countdown(n):
    while n > 0:
        yield n
        n -= 1
# 创建生成器对象
generator = countdown(5)
# 通过迭代生成器获取值
print(next(generator))  # 输出: 5
print(next(generator))  # 输出: 4
print(next(generator))  # 输出: 3
# 使用 for 循环迭代生成器
for value in generator:
    print(value)  # 输出: 2 1

def 函数名（参数列表）:
    函数体

# 可写函数说明
def changeme( mylist ):
   "修改传入的列表"
   mylist.append([1,2,3,4])
   print ("函数内取值: ", mylist)
   return
# 调用changeme函数
mylist = [10,20,30]
changeme( mylist )
print ("函数外取值: ", mylist)//地址没有变

def printme( str ):
   "打印任何传入的字符串"
   print (str)
   return 
printme( str = "菜鸟教程")

def functionname([formal_args,] *var_args_tuple ):
   "函数_文档字符串"
   function_suite
   return [expression]

def printinfo( arg1, *vartuple ):
   "打印任何传入的参数"
   print ("输出: ")
   print (arg1)
   print (vartuple)
printinfo( 70, 60, 50 )

def printinfo( arg1, **vardict ):
   "打印任何传入的参数"
   print ("输出: ")
   print (arg1)
   print (vardict)
printinfo(1, a=2,b=3)

lambda arguments: expression

f = lambda: "Hello World!"
print(f())

x = lambda a, b : a * b
print(x(5, 6))

f = open("/tmp/foo.txt", "w")
num = f.write( "Python 是一个非常好的语言。\n是的，的确非常好!!\n" )
print(num)
f.close() #输出结果为29

f = open("/tmp/foo1.txt", "w")
value = ('www.runoob.com', 14)
s = str(value)
f.write(s)
f.close()

>>> with open('/tmp/foo.txt', 'r') as f:
...     read_data = f.read()
>>> f.closed
True

x = 10
if x > 5:
    raise Exception('x 不能大于 5。x 的值为: {}'.format(x))

with open("myfile.txt") as f:
    for line in f:
        print(line, end="")

class people:
    name = ''
    age = 0
    #定义私有属性,私有属性在类外部无法直接进行访问
    __weight = 0
    def __init__(self,n,a,w):
        self.name = n
        self.age = a
        self.__weight = w
    def speak(self):
        print("%s 说: 我 %d 岁。" %(self.name,self.age))
p = people('runoob',10,30)
p.speak()

class student(people):
    grade = ''
    def __init__(self,n,a,w,g):
        #调用父类的构造函数
        people.__init__(self,n,a,w)
        self.grade = g
    #覆写父类的方法
    def speak(self):
        print("%s 说: 我 %d 岁了，我在读 %d 年级"%(self.name,self.age,self.grade))

多继承的类定义：class DerivedClassName(Base1, Base2, Base3)：

num = 1
def fun1():
    global num  # 需要使用 global 关键字声明
    print(num) 
    num = 123
    print(num)
fun1()
print(num)

def outer():
    num = 10
    def inner():
        nonlocal num   # nonlocal关键字声明
        num = 100
        print(num)
    inner()
    print(num)
outer()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import requests
import json
if __name__ == "__main__":
    #1.指定url
    post_url = 'https://movie.douban.com/j/chart/top_list'
    #2.进行UA伪装
    headers = {
        'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36'
    }
    param = {
        'type': '24',
        'interval_id': '100:90',
        'action': '',
        'start': '0',  # 从库中的第几部电影去取
        'limit': '20',  # 一次取出的个数
    }
    response = requests.get(post_url, headers=headers, params=param)
    list_data = response.json()
    fp = open('./douban.json', 'w', encoding='utf-8')
    json.dump(list_data, fp=fp, ensure_ascii=False)
    print('over!!!')
}

app = Flask(__name__, template_folder='my_templates')