第三讲 程序设计基础

a = "Hello"
b = "Python"
 
print("a + b 输出结果：", a + b)
print("a * 2 输出结果：", a * 2)
print("a[1] 输出结果：", a[1])
print("a[1:4] 输出结果：", a[1:4])
# in 
if( "H" in a) :
    print("H 在变量 a 中")
else :
    print("H 不在变量 a 中")
#not in 
if( "M" not in a) :
    print("M 不在变量 a 中")
else :
    print("M 在变量 a 中")
# r R 直接打印字符串 
print (r'\n')
print (R'\n')

tup1 = ('Google', 'Runoob', 1997, 2000)
tup2 = (1, 2, 3, 4, 5 )
tup3 = "a", "b", "c", "d"   #  不需要括号也可以
type(tup3)
print(tup1,"\n","tup2","\n",tup3,"\n",type(tup3))

print(id(tup1))
tup1=1,2,3
print(id(tup1))

list = ['red', 'green', 'blue', 'yellow', 'white', 'black']
print( list[0] )
print( list[-2] )
print( list[-1] )

list = ['Google', 'Runoob', "Zhihu", "Taobao", "Wiki"]
 
# 读取第二位
print ("list[0]: ", list[0])
# 从第二位开始（包含）截取到倒数第二位（不包含）
print ("list[0:4]: ", list[0:5])

#
list[2] = 2001
print ("更新后的第三个元素为 : ", list)
 
list.append('Baidu')
print ("更新后的列表 : ", list)

list[:]=''

print(list)

#删除元素
del list[2]
print ("删除第三个元素 : ", list)

# A function that returns the length of the value:
def myFunc(e):
  return len(e)
cars = ['Ford', 'Mitsubishi', 'BMW', 'VW']
cars.sort(reverse=True, key=myFunc)
print(cars)

cars.pop()
print(cars)

basket = {'apple', 'orange', 'apple', 'pear', 'orange', 'banana'}
print(len(basket))                      # 这里演示的是去重功能

{'orange', 'banana', 'pear', 'apple'}
'orange' in basket                 # 快速判断元素是否在集合内

'crabgrass' in basket

# 下面展示两个集合间的运算.
a = set('abracadabra')
b = set('alacazam')
print('a=',a)
print('b=',b)
# 集合a中包含而集合b中不包含的元素                                 
a - b                              

# 集合a或b中包含的所有元素（并集）
a | b                              

# 集合a和b中都包含了的元素(交集)
a & b                              

# 不同时包含于a和b的元素（交集的补集）
a ^ b                              

#类似列表推导式，同样集合支持集合推导式(Set comprehension):
a = {x  for x in 'abracadabra' if x not in 'abc'}
print(a)

# 增加
basket.add("Facebook")
print(basket)
# 添加
basket.update("Facebook")
print(basket)
# 删除
#basket.remove("apple")
print(basket)
#basket.remove('none')  # throw error!!!
basket.discard('none') # don't throw error!!!
basket.pop()# throw one element random

# 计算集合长度
basket.pop()
print(basket)
len(basket)

#清理集合
basket.clear()

import graphviz
dot=graphviz.Digraph(comment='the round table',name="顺序结构",node_attr={'shape': 'box'})
dot.node('1','字典')
dot.node('2','name1：')
dot.node('3','key2：')
dot.node('4','key3：')
dot.node('5','Value1')
dot.node('6','Value2')
dot.node('7','Value3')
dot.edges(['12','13','14','25','36','47'])
dot

dict = {'name': 'zhangsan', 'Age': 20, 'url': 'www.xauat.edu.cn'}
print(dict)

dict['name']

dict['name']="李四"
dict['sex']='男'
print(dict)

car = {
  'brand': 'Ford',
  'model': 'Mustang',
  'year': 1964
}
x = car.items()
car['year'] = 2018
print(x)

car.keys()

x = True
country_counter = {}

def addone(country):
    if country in country_counter:
        country_counter[country] += 1
    else:
        country_counter[country] = 1

addone('China')
addone('Japan')
addone('china')

print(len(country_counter))