变量与基本类型

x = 1
y = (x = x + 1) # 赋值语句不是合法表达式
y = x = x + 1 # 链式赋值
x += 1 # 增量赋值
x = y = z = 1 # 多重赋值
(x,y,z) = (1,2,'a string') # mul-tuple "多元"赋值

# Python中交换值
(x,y) = (1,2)
(x,y) = (y,x)

import this

Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
Sparse is better than dense.
Readability counts.
Special cases aren't special enough to break the rules.
Although practicality beats purity.
Errors should never pass silently.
Unless explicitly silenced.
In the face of ambiguity, refuse the temptation to guess.
There should be one-- and preferably only one --obvious way to do it.
Although that way may not be obvious at first unless you're Dutch.
Now is better than never.
Although never is often better than *right* now.
If the implementation is hard to explain, it's a bad idea.
If the implementation is easy to explain, it may be a good idea.
Namespaces are one honking great idea -- let's do more of those!

# !/usr/bin/python  --> 无需直接调用解释器，输入脚本名字即可执行
# -*- coding: utf-8 -*-   --> module.__doc__ 访问
# __author__:  reworld

# (1) 起始行 ⬆

#（2）模块文档
'''this is a templete module'''

# (3) 模块导入
import sys
import os

# (4) (全局)变量定义
debug = True           # 除非必须  尽量使用局部变量代替全局变量 易维护节约内存

# (5) 类定义(若有)
class FooClass(object):
    "Foo Class"   # class.__doc__ 模块被导入时
    pass

# (6) 函数定义(若有)
def test():
    "test function"  # function.__doc__
    foo = FooClass()
    if debug:
        print("ran test()")
    pass
# (7) 主程序
if __name__ == "__main__":  
    test() # 通常调用main函数

x = 4
print(x)

del obj1[,obj2[,...bojN]]

# coding=utf-8
# !/usr/bin/python

'makeTextFile.py -- create text file'

import os

ls = os.linesep # 本地变量别名

fname = raw_input("\nplease input filename\n")

all = []
print("\nEnter lines ('.' by itself to quit).\n")

while True:
    entry = raw_input(">")
    if entry == '.':
        break
    else:
        all.append(entry)

fobj = open(fname,'w')
fobj.writelines(['%s%s' % (x, ls) for x in all])
fobj.close()
print('DONE')

# !/usr/bin/python
# -*- coding: utf-8 -*-
# __author__:  reworld


'readTextFile.py -- read and display text file'

fname = raw_input('Enter filename:')
print()

# try-except-else用法
try:
    fobj = open(fname,'r')
except IOError, e:
    # 文件不存在已经包含在该异常内
    # TODO 如何做文件名打印 file:%s
    print("*** file open error:", e)
else: # 此处else用法
    for eachLine in fobj:
        print(eachLine)
    fobj.close()

# 内建函数type()
type(42)
<type 'int'> # 类型对象
type(type(42))
<type 'type'>

# 编译过的Python源代码片段，是可执行对象
compile()  exec()  eval()

# !/usr/bin/python
# -*- coding: utf-8 -*-
# __author__:  reworld

if __name__ == "__main__":
    foo_str = 'abcde'
    # 语法sequence[起始索引:结束索引:步进值]
    print(foo_str[::-1])
    # edcba
    print(foo_str[::-2])
    # eca

# !/usr/bin/python
# -*- coding: utf-8 -*-
# __author__:  reworld

if __name__ == "__main__":
	# 数值类型根据数值的大小和符号比较，字符串按照字符序列值进行比较
    print(2 == 2)
    print(2.46 <= 2)
    # print(5+4j < 2 -3j)  报错
    print([3, 'abc'] == ['abc', 3])

    # 多个比较操作放在同一行进行，求值顺序从左到右
    print(3 < 4 < 5)
    print(3 > 2 > 5 !=2)

    foo1 = 4.3
    foo2 = foo1
    foo3 = 4.3
    foo4 = 1 + 3.3
    print(id(foo1),id(foo2),id(foo3),id(foo4))
    a is b ==> id(a) == id(b) # 同一个对象
    a is not b # 不是同一个对象
    # (140480586453024, 140480586453024, 140480586453024, 140480584254600)
        foo5 = 1
    foo6 = 1
    if (foo5 is foo6):
        print("same obj")
    else:
        print("diff obj")
    # same obj

	# !/usr/bin/python
# -*- coding: utf-8 -*-
# __author__:  reworld

if __name__ == "__main__":
    print(type(""))
    print(type(100))
    print(type(1.0))
    print(type([]))
    print(type(()))
    print(type({}))
    print(type(type))

    class Foo: pass

    foo = Foo()
    print(type(Foo))
    print(type(foo))

    class Bar(object):pass

    bar = Bar()

    print(type(Bar),type(bar))
 
<type 'str'>
<type 'int'>
<type 'float'>
<type 'list'>
<type 'tuple'>
<type 'dict'>
<type 'type'>
<type 'classobj'>
<type 'instance'>
(<type 'type'>, <class '__main__.Bar'>)  -- > 注意此处结果

# !/usr/bin/python
# -*- coding: utf-8 -*-
# __author__:  reworld

"""check num type"""

def checkNumType(num):
    print num,"is",
    if isinstance(num, (int, long, float, complex)):
        print 'a number of type:', type(num).__name__
    else:
        print 'not a number at all!'

if __name__ == "__main__":
    checkNumType(5)