简单的python入门语法

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#!/usr/bin/python3

# 开始学习python
print("hello,world")

# 条件语句
a,b = 3,1
if a < b:
	print('a({}) is less than b({})'. format(a,b))
else:
	print('a({}) is great than b({})'. format(a,b))

# ?: 模仿三元表达式
print("foo" if a < b else "bar");

# while循环 fabonacci
a,b = 0,1 # 赋值 a = 0,b = 1

while b < 50:
	print(b)
	a,b = b,a+b

print("Done.")	

# for循环，迭代输出文本信息
#lines.txt
#01 This is a line of text
#02 This is a line of text
#03 This is a line of text
#04 This is a line of text
#05 This is a line of text

fh = open("lines.txt")
for line in fh.readlines():
	print(line,end='')

# 计算素数的函数，素数（只能被1和自己整除的数）
def isprime(n):
	if n == 1:
		#print("1 is special")
		return False
	for x in range(2,n):
		if n%x == 0:
			#print("{} equals {} x {}".format(n,x,n // x))
			return False
	else:
		#print(n,"is a prime")
		return True

for n in range(1,30):
	isprime(n)

# 迭代函数 primes,phper表示很难理解.
# yield返回当前的素数，primes下次迭代时，将会从yield返回的数字开始。

def primes(n = 1):
	while(True):
		if isprime(n): yield n
		n += 1

for n in primes():
	if n > 100: break
	print(n)

# oop 基本类的定义
class Fibonacci():
	def __init__(self,a,b):
		self.a = a
		self.b = b
	# 含有yield语法的应该都是一个构造器，可以内部迭代
	def series(self):
		while (True):
			yield(self.b)
			self.a,self.b = self.b,self.a + self.b

# 迭代构造器 Fibonacci.series()
f = Fibonacci(0,1)
for r in f.series():
	if r > 100: break
	print(r,end=' ')

# 一个简单的mvc模式
# oop2 继承与多态，高级概念
# Duck,Person,Dog都继承AnimalActions

# --- VIEW ---
class AnimalActions:
	def quack(self): return self._doAction('quack')
	def feathers(self): return self._doAction('feathers')
	def bark(self): return self._doAction('bark')
	def fur(self): return self._doAction('fur')

	def _doAction(self,action):
		if action in self.strings:
			return self.strings[action]
		else:
			return "The {} has no {}".format(self.animalName(),action)

	def animalName(self):
		return self.__class__.__name__.lower()

# --- MODEL ---
class Duck(AnimalActions):
	strings = dict(
		quack = "Quaaaak!",feathers = "The duck has gray and white feathers."		
	)

class Person(AnimalActions):
 	strings = dict(
		quack = "The person iitates a duck!",feathers = "The person takes a feather from the ground and shows it.",bark = "The person says woof.",fur = "The person puts on a fur coat."
	)

class Dog(AnimalActions):
    strings = dict(        
        bark = "Arf!",fur = "The dog has white fur with black spots."
    )

# --- CONTROLLER ---
def in_the_doghouse(dog):
	print(dog.bark())
	print(dog.fur())

def in_the_forest(duck):
	print(duck.quack())
	print(duck.feathers())

def main():
	donald = Duck()
	john = Person()
	fido = Dog()
    # 三个对象都能在不同的地方拥有同样的行为
	print("- In the forest:")
	for o in ( donald,john,fido ):
		in_the_forest(o)

	print("- In the doghouse:")
	for o in ( donald,fido ):
		in_the_doghouse(o)
 
if __name__ == '__main__': main()

# 异常 phper表示很强大
# 尝试打开一个不存在的文件
try:
	fh = open("xline.txt")
	for line in fh.readlines():
		print(line)
except IOError as e:
	print("something bad happend {}.".format(e))

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