# 过滤偶数
def is_odd(n):
return n % 2 == 1
L = list(filter(is_odd, [1, 2, 3, 4, 5]))
print(L)
# 用filter求素数
def _odd_iter():
n = 1
while True:
n = n + 2
yield n
def _not_divisible(n):
return lambda x: x % n >0
def primes():
yield 2
it = _odd_iter() # 初始序列
while True:
n = next(it) # 返回序列的第一个对象
yield n
it = filter(_not_divisible(n), it) # 构造新序列
for n in primes():
if n < 1000:
print(n)
else:
break
# 写一个hello的模块
import sys
def test():
args = sys.argv
if len(args) == 1:
print('hello world')
elif len(args) == 2:
print('Hello, %s' % args[1])
else:
print('Too many arguments!')
if __name__ == '__main__':
test()
# 以_或__开头的函数默认内部使用
def _private_1():
return 'Hello, %s' % name
def _private_2():
return 'Hi, %s' % name
def greeting(name):
if len(name) > 3:
return _private_1(name)
else:
return _private_2(name)
print(greeting('Michael'))
# 缩略图生成
from PIL import Image
def thumbnail_generator(mdic):
im = Image.open(mdic)
size = 128, 128 #定义一个元组
print(im.format, im.size, im.mode) #png (540, 258) P
if im.mode != 'RGB':
im = im.convert('RGB') #mode!='RGB'时要转化为RGB,否则生成JPG缩略图报错
im.thumbnail(size)
im.save('thumb.jpg', 'JPEG')
thumbnail_generator('test.jpg')
# 函数实现
std1 = {'name': 'Michael', 'score': 98}
std2 = {'name': 'Bob', 'score': 81}
def print_score(std):
print('%s: %s' %(std['name'], std['score']))
print_score(std2)
# 面向对象实现
class Student(object):
def __init__(self, name, score):
self.name = name
self.__score = score # __表示类私有的
def print_score(self):
print('%s: %s' %(self.name, self.score))
bart = Student('Bart Simpson', 59)
lisa = Student('Lisa Simpson', 87)
bart.print_score()
lisa.print_score()
# 类的继承和多态
class Animal(object):
def run(self):
print('Animal is running...')
class Dog(Animal):
def run(self):
print('Dog is running..')
class Cat(Animal):
def run(self):
print('Cat is running..')
dog = Dog()
dog.run()
cat = Cat()
cat.run()
# 从文件流中读取图像
def readImg(fp):
if(hasattr()):
print(readData(fp))
print(None)
readImg('test.jpg')
# 使用get和set
class Student(object):
def get_score(self):
return self._score
def set_score(self, value):
if not isinstance(value, int):
raise ValueError('score must be an integer!')
if value < 0 or value > 100:
raise ValueError('score must between 0 ~ 100!')
self._score = value
s = Student()
s.set_score(60)
print(s.get_score())
s.set_score(9999) # 报错
# 多重继承
class Animal(object):
pass
# 大类
class Mammal(Animal):
pass
class Bird(Animal):
pass
# 各种动物
class Dog(Mammal):
pass
class Bat(Mammal):
pass
class Parrot(Bird):
pass
class Ostrish(Bird):
pass
# 再加上Runnable和Flyable功能
class Runnable(object):
def run(self):
print('Running...')
class Flyable(self):
def fly(self):
print('Flying...')
# 对于需要Runnable功能的
class Bat(Mammal, Runnable):
pass
# 使用错误码来表示是否出错, 其实十分不便
def foo():
r = some_function()
if r == (-1):
return (-1)
# do something
return r
def bar():
r = foo()
if r = (-1):
print('Error')
else:
pass
# try...except...finally...错误处理机制
try:
print('try...')
r = 10 / 0
print('result:', r)
except ZeroDivisionError as e:
print('except:', e)
finally:
print('finally...')
print('END')
# 多个except来捕获不同类型的错误
try:
print('try...')
r = 10 / int('a')
print('result:', r)
except ValueError as e:
print('ValueError:', e)
except ZeroDivisionError as e:
print('ZeroDivisionError', e)
finally:
print('finally...')
print('END')
# 调用堆栈, 错误一直往上抛
def foo(s):
return 10 / int(s)
def bar(s):
return foo(s) * 2
def main():
bar('0')
main()
# 执行错误抛出后，继续运行
class FooEffor(ValueError):
pass
def foo(s):
n = int(s)
if n==0:
raise FooError('invalid value:%s' % s)
return 10 /n
foo('0')
# 1. 简单直接粗暴, 把可能有问题的变量打印出来
def foo(s):
n = int(s)
print('>>> n = %d' %n)
print 10 / n
def main():
foo('0')
main()
# 2.凡是print()来辅助查看的地方, 都可以用断言(assert)来替代s
def foo(s):
assert n != 0, 'n is zero'
return 10 / n
def main():
foo('0')
main()
# 3.logging不会抛出错误,而且可以输出到文件
import logging
logging.basicConfig(level=logging.INFO)
s = '0'
n = int(s)
logging.info('n = %d' % n)
print(10 / n)
# 编写单元测试
import unittest
from mydict import Dict
class TestDict(unittest.TestCase):
def setUp(self):
print('setUp...')
def tearDown(self):
print('tearDown...')
def test_init(self):
self.assertEqual(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()
# 访问数据库
SQLlite
# mysql
# 导入mysql驱动
import mysql.connector
# 注意把password设为你的root口令
conn = mysql.connector.connect(user='root', password='123456', database='test')
cursor = conn.cursor()
# 创建user表
cursor.excute('create table user (id varchar(20) primary key, name varchar(20))')
# 插入一行记录, 记住mysql的占位符是%s
cursor.excute('insert into user(id, name) value(%s, %s)', ['1', 'lei.sun'])
cursor.rowcount
# 提交事务
conn.commit()
cursor.close()
# 运行查询
cursor = conn.cursor()
cursor.excute('select * from user where id = %s', ('1', ))
values = cursor.fetchall()
values