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python（六）类、文件读写、发邮件

阅读：719 发布：2018-04-23 作者：lypeng

# 类
1. 类定义的时候，可以传一个参数，object表示基类，其他则表示继承了该类
2. 类，__init__初始化方法
3. 类中的所有方法第一个参数是self
4. 私有化变量，前面加两个下划线
5. __slots__ 表示只允许外部绑定的属性
6. 类中的特殊方法，__iter__迭代
7. getattr()、setattr()以及hasattr()属性相关

## example1
```python
class Student(object):
    __slots__ = ('name', 'gender') # 用tuple定义允许绑定的属性名称
    def __init__(self, name, gender):
        self.name = name
        self.__gender = gender
    def set_gender(self,gender):
        if gender=='male' or gender=='female':
            self.__gender = gender
        else:
            raise ValueError('bad value')
    def get_gender(self):
        return self.__gender

bart = Student('Bart', 'male')
if bart.get_gender() != 'male':
    print('测试失败!')
else:
    bart.set_gender('female2')
    if bart.get_gender() != 'female':
        print('测试失败!')
    else:
        print('测试成功!')
```

## example2 使用生成器函数实现可迭代对象，for循环迭代素数

```python
class PrimeNumbers:
    def __init__(self,start,end):
        self.start = start
        self.end = end
    def isPrimeNum(self,k):
        if k<2:
            return False
        else:
            for i in range(2,k-1):
                if k%i == 0:
                    return False
        return True
    def __iter__(self):
        for k in range(self.start,self.end+1):
            if self.isPrimeNum(k):
                yield k
for x in PrimeNumbers(1,100):
    print(x)
```

```python
# 浮点数迭代器
class FloatIter:
    def __init__(self,start,end,step=0.1):
        self.start = start
        self.end = end
        self.step = step

def __iter__(self):
        t = self.start
        while t<=self.end:
            yield t
            t += self.step

def __reversed__(self):
        t = self.end
        while t>=self.start:
            yield t
            t -= self.step

for i in FloatIter(1.0,4.0,0.5):print(i)
for i in reversed(FloatIter(1.0,4.0,0.5)):print(i)
```

## 其他属性
```python
# getattr()、setattr()以及hasattr()
>>> class MyObject(object):
...     def __init__(self):
...         self.x = 9
...     def power(self):
...         return self.x * self.x
...
>>> obj = MyObject()
>>> hasattr(obj, 'x') # 有属性'x'吗？
True
>>> obj.x
9
>>> hasattr(obj, 'y') # 有属性'y'吗？
False
>>> setattr(obj, 'y', 19) # 设置一个属性'y'
>>> hasattr(obj, 'y') # 有属性'y'吗？
True
>>> getattr(obj, 'y') # 获取属性'y'
19
>>> obj.y # 获取属性'y'
19
>>> getattr(obj, 'z', 404) # 获取属性'z'，如果不存在，返回默认值404
404
```

-----------

# 文件读写

```python
#!/usr/bin/python3
# -*- coding: utf-8 -*-

# 文件操作
# filepath = '/home/wwwroot/test/python/w.txt'

# f = open(filepath,'r',encoding='utf-8',errors='ignore')
# f.read()
# f.clode()

# try:
#     f = open(filepath, 'r')
#     print(f.read())
# finally:
#     if f:
#         f.close()

# with open(filepath, 'r') as f:
#     print(f.read())

# 调用read(size)方法，每次最多读取size个字节的内容。
# 调用readline()可以每次读取一行内容，
# 调用readlines()一次读取所有内容并按行返回list。

# with open(filepath, 'r') as f:
#     print(f.readline()) #读取一行

# 'a'是追加，w+不起作用

# 'r'	open for reading (default)
# 'w'	open for writing, truncating the file first
# 'x'	open for exclusive creation, failing if the file already exists
# 'a'	open for writing, appending to the end of the file if it exists

# 'b'	binary mode
# 't'	text mode (default)
# '+'	open a disk file for updating (reading and writing)
# 'U'	universal newlines mode (deprecated)

# with open('/home/wwwroot/test/python/w.txt','a') as f:
#     f.write('write file learning222...')
#     f.close()

# with open(filepath, 'r') as f:
#     for line in f.readlines():
#         print(line.strip())

# StringIO
# >>> from io import StringIO
# >>> f = StringIO()
# >>> f.write('hello')
# 5
# >>> f.write(' ')
# 1
# >>> f.write('world!')
# 6
# >>> print(f.getvalue())
# hello world!

# 目录操作

# >>> os.mkdir('/home/wwwroot/test/ttt')
# >>> os.path.abspath('.')
# '/home/lypeng'
# os.rmdir('/home/wwwroot/test/ttt')
# >>> os.path.split('/home/wwwroot/test/python/k.txt')
# ('/home/wwwroot/test/python', 'k.txt')
# >>> os.path.splitext('/home/wwwroot/test/python/k.txt')
# ('/home/wwwroot/test/python/k', '.txt')
# # 对文件重命名:
# >>> os.rename('test.txt', 'test.py')
# # 删掉文件:
# >>> os.remove('test.py')

# 显示当前目录下后缀是.py的文件
# [x for x in os.listdir('.') if os.isfile(x) and os.splitext(x)[1]=='.py']

#json与字典转换，json.dumps(dict)；json.loads(str)
>>> import json
>>> d = dict(name='Bob', age=20, score=88)
>>> json.dumps(d)
'{"age": 20, "score": 88, "name": "Bob"}'

>>> json_str = '{"age": 20, "score": 88, "name": "Bob"}'
>>> json.loads(json_str)
{'age': 20, 'score': 88, 'name': 'Bob'}
```

# 发邮件
安装模块 `pip3 install yagmail`
具体说明参见：https://github.com/kootenpv/yagmail?_blnak
```python
#!/usr/bin/python3
# -*- coding: utf-8 -*-
import yagmail
yag = yagmail.SMTP(user='893371810@qq.com', password='mima', host='smtp.qq.com', port='465')
# contents = ['html', '/home/wwwroot/dpshop/a.mp3']
yag.send('893371810@qq.com', "subjects", '<b>This is the body, and here is just text</b>')

# 发送给谁可以写多个，用list或者tuple，contents可以是个list，可以是字符串，HTML，本地文件绝对地址，如果有本地元素且文件存在，会被当做附件，否则当字符串处理
```

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