python3 笔记

# -*- coding: cp-1252 -*-

>>> import keyword
>>> keyword.kwlist
['False', 'None', 'True', 'and', 'as', 'assert', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']

#这是单行注释

'''这是多行注释
这是多行注释
'''

if True:
	print ("True")
else:
	print ("False")

if True:
    print ("Answer")
    print ("True")
else:
    print ("Answer")
  print ("False")    # 缩进不一致，会导致运行错误

 File "test.py", line 6
    print ("False")    # 缩进不一致，会导致运行错误
                                      ^
IndentationError: unindent does not match any outer indentation level

total = item_one + \
        item_two + \
        item_three

total = ['item_one', 'item_two', 'item_three',
        'item_four', 'item_five']

word = '字符串' '\n'
sentence = "这是一个句子。" '\n'
paragraph = """这是一个段落，
可以由多行组成""" '\n'

print(word + sentence + paragraph)

s =  input("\n\n按下 结束输入 继续。")
print(s)

import sys; x = 'runoob'; sys.stdout.write(x + '\n')

if expression : 
   suite
elif expression : 
   suite 
else : 
   suite

x="a"
y="b"
# 换行输出
print( x )
print( y )

print('---------')
# 不换行输出
print( x, end=" " )
print( y, end=" " )
print()

# 格式化输出，类似于c的printf
print ("我叫 %s 今年 %d 岁!" % ('小明', 10))

import sys
print('================Python import mode==========================');
print ('命令行参数为:')
for i in sys.argv:
    print (i)
print ('\n python 路径为',sys.path)

from sys import argv,path  #  导入特定的成员
 
print('================python from import===================================')
print('path:',path) # 因为已经导入path成员，所以此处引用时不需要加sys.path

$ python -h
usage: python [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-c cmd : program passed in as string (terminates option list)
-d     : debug output from parser (also PYTHONDEBUG=x)
-E     : ignore environment variables (such as PYTHONPATH)
-h     : print this help message and exit

[ etc. ]

# 如下实例，查看 max 内置函数的参数列表和规范的文档
>>> help(max)
……显示帮助信息……

>>> print(max.__doc__)    # 注意，doc的前后分别是两个下划线
max(iterable, *[, default=obj, key=func]) -> value
max(arg1, arg2, *args, *[, key=func]) -> value

With a single iterable argument, return its biggest item. The
default keyword-only argument specifies an object to return if
the provided iterable is empty.
With two or more arguments, return the largest argument.

#验证标识符
a=1
_b1 = 2
变量 = 3

print (a)
print (_b1)
print (变量)

# 验证保留字
import keyword
print (keyword.kwlist)

#这是单行注释
'''这是多行注释
这是多行注释
'''

#行与缩进
if True:
    print ("True")
else:
    print ("False")

if True:
    print ("Answer")
    print ("True")
else:
    print ("Answer")
  #print ("False")    # 缩进不一致，会导致运行错误


#多行语句
total = "1" + \
        "2" + \
        "3"
#在 [], {}, 或 () 中的多行语句，不需要使用反斜杠(\)，例如：
total = ['item_one', 'item_two', 'item_three',
        'item_four', 'item_five']

#数据类型
a = 1 #整数
b = 10000000000000 #长整数
c = 1.23 #浮点数
d = 1 + 2j #复数

print(a)
print(b)
print(c)
print(d)

word = '字符串' '\n'
sentence = "这是一个句子。" '\n'
paragraph = """这是一个段落，
可以由多行组成""" '\n'

print(word + sentence + paragraph)

s =  input("\n\n按下 结束输入 继续。")
print(s)


import sys; x = 'runoob'; sys.stdout.write(x + '\n')


'''
缩进相同的一组语句构成一个代码块，我们称之代码组。
像if、while、def和class这样的复合语句，首行以关键字开始，以冒号( : )结束，该行之后的一行或多行代码构成代码组。
我们将首行及后面的代码组称为一个子句(clause)。
'''


#Print 输出
x="a"
y="b"
# 换行输出
print( x )
print( y )

print('---------')
# 不换行输出
print( x, end="" )
print( y, end="" )
print()


#import 与 from...import
import sys
print('================Python import mode==========================');
print ('命令行参数为:')
for i in sys.argv:
    print (i)
print ('\n python 路径为',sys.path)


from sys import argv,path  #  导入特定的成员
 
print('================python from import===================================')
print('path:',path) # 因为已经导入path成员，所以此处引用时不需要加sys.path

counter = 100          # 整型变量
miles   = 1000.0       # 浮点型变量
name    = "runoob"     # 字符串
 
print (counter)
print (miles)
print (name)

a = b = c = 1
print(a,b,c)
a, b, c = 1, 2, "runoob"
print(a,b,c)

a, b, c, d = 20, 5.5, True, 4+3j
print(type(a), type(b), type(c), type(d))

a = 111
print(isinstance(a, int))

class A:
    pass

class B(A):
    pass

isinstance(A(), A)  # returns True
type(A()) == A      # returns True
isinstance(B(), A)    # returns True
type(B()) == A        # returns False

var1 = 1
var2 = 10

del var1[,var2[,var3[....,varN]]]]

#创建Number对象
var1 = 1
var2 = 10
print(var1,var2)
#删除一些对象引用
del var1,var2
print(var1,var2) #报错：NameError: name 'var1' is not defined

>>>5 + 4  # 加法
9
>>> 4.3 - 2 # 减法
2.3
>>> 3 * 7  # 乘法
21
>>> 2 / 4  # 除法，得到一个浮点数
0.5
>>> 2 // 4 # 除法，得到一个整数
0
>>> 17 % 3 # 取余 
2
>>> 2 ** 5 # 乘方

变量[头下标:尾下标]

str = 'abcdef'
print (str)          # 输出字符串
print (str[0:-1])    # 输出第一个到倒数第二个的所有字符
print (str[0])       # 输出字符串第一个字符
print (str[2:5])     # 输出从第三个开始到第五个的字符
print (str[2:])      # 输出从第三个开始的后的所有字符
print (str * 2)      # 输出字符串两次
print (str + "TEST") # 连接字符串

print('Ru\noob')
print(r'Ru\noob')

word = 'Python'
print(word[0], word[5])
print(word[-1], word[-6])

变量[头下标:尾下标]

list = [ 'abcd', 786 , 2.23, 'runoob', 70.2 ]
tinylist = [123, 'runoob']
 
print (list)            # 输出完整列表
print (list[0])         # 输出列表第一个元素
print (list[1:3])       # 从第二个开始输出到第三个元素
print (list[2:])        # 输出从第三个元素开始的所有元素
print (tinylist * 2)    # 输出两次列表
print (list + tinylist) # 连接列表

a = [1, 2, 3, 4, 5, 6]
a[0] = 9
a[2:5] = [13, 14, 15]
a[2:5] = []   # 删除
print(a)

tuple = ( 'abcd', 786 , 2.23, 'runoob', 70.2  )
tinytuple = (123, 'runoob')
 
print (tuple)             # 输出完整元组
print (tuple[0])          # 输出元组的第一个元素
print (tuple[1:3])        # 输出从第二个元素开始到第三个元素
print (tuple[2:])         # 输出从第三个元素开始的所有元素
print (tinytuple * 2)     # 输出两次元组
print (tuple + tinytuple) # 连接元组

tup = (1, 2, 3, 4, 5, 6)
print(tup[0])
print(tup[1:5])

tup[0] = 11  # 修改元组元素的操作是非法的，TypeError: 'tuple' object does not support item assignment

tup1 = ()    # 空元组
tup2 = (20,) # 一个元素，需要在元素后添加逗号

student = {'Tom', 'Jim', 'Mary', 'Tom', 'Jack', 'Rose'}
print(student)   # 输出集合，重复的元素被自动去掉
 
# 成员测试
if('Rose' in student) :
    print('Rose 在集合中')
else :
    print('Rose 不在集合中')
 
 
# set可以进行集合运算
a = set('abracadabra')
b = set('alacazam')
 
print(a)
print(b)
print(a - b)     # a和b的差集
print(a | b)     # a和b的并集
print(a & b)     # a和b的交集
print(a ^ b)     # a和b中不同时存在的元素

dict = {}
dict['one'] = "1 - 菜鸟教程"
dict[2]     = "2 - 菜鸟工具"
tinydict = {'name': 'runoob','code':1, 'site': 'www.runoob.com'}
 
print (dict['one'])       # 输出键为 'one' 的值
print (dict[2])           # 输出键为 2 的值
print (tinydict)          # 输出完整的字典
print (tinydict.keys())   # 输出所有键
print (tinydict.values()) # 输出所有值

dict([('Runoob', 1), ('Google', 2), ('Taobao', 3)])
{x: x**2 for x in (2, 4, 6)}
dict(Runoob=1, Google=2, Taobao=3)

if('a' in 'abc'):
    print("True") #返回true

if('abc' in ['abc','fwer']):
    print("True") #返回true

if 条件1:
    语句块1
elif 条件2:
    语句块2
else:
    语句块3

while 条件：
    语句块

for 变量 in 序列:
    语句块
else:
    语句块

range(start, end,step)

for i in range(5):
    print(i)
    
for i in range(5,9) :
    print(i)

while True:
    pass  # 等待键盘中断 (Ctrl+C)

class MyEmptyClass:
    pass


for letter in 'Runoob': 
    if letter == 'o':
        pass
        print ('执行 pass 块')
    print ('当前字母 :', letter)

print ("Good bye!")

list=[1,2,3,4]
it = iter(list)    # 创建迭代器对象
for x in it:
    print (x, end=" ")
		
		
import sys         # 引入 sys 模块

list=[1,2,3,4]
it = iter(list)    # 创建迭代器对象

while True:
    try:
        print (next(it))
    except StopIteration:
        sys.exit()

def fibonacci(n): # 生成器函数 - 斐波那契
    a, b, counter = 0, 1, 0
    while True:
        if (counter > n): 
            return
        yield a
        a, b = b, a + b
        counter += 1
				
f = fibonacci(10) # f 是一个迭代器，由生成器返回生成

for i in f:
    print(i)

def 函数名（参数列表）:
    函数体

def printme( str ):
    "打印任何传入的字符串"
    print (str);
    return

printme("我要调用用户自定义函数!")

def changeNum(num):
    num = 2

def changeStr(str):
    str = "b"

def changeObject(list):
    list = [2]

def changeObjectValue(list):
    list[0] = 2


num = 1
changeNum(num)
print (num)

str = "a"
changeStr(str)
print (str)

list = [1]
changeObject(list)
print(list)

changeObjectValue(list)
print(list)

1
a
[1]
[2]

lambda [arg1 [,arg2,.....argn]]:expression

# 可写函数说明
sum = lambda arg1, arg2: arg1 + arg2;
 
# 调用sum函数
print ("相加后的值为 : ", sum( 10, 20 ))
print ("相加后的值为 : ", sum( 20, 20 ))

x = int(2.9)  # 内建作用域
 
g_count = 0  # 全局作用域
def outer():
    o_count = 1  # 闭包函数外的函数中
    def inner():
        i_count = 2  # 局部作用域

num = 1
def fun1():
    global num  # 需要使用 global 关键字声明，否则下面修改num的值
    print(num) #此句将报错
    num = 123
    print(num)
fun1()

def outer():
    num = 10
    def inner():
        nonlocal num   # nonlocal关键字声明
        num = 100
        print(num)
    inner()
    print(num)
outer()

>>> stack = [3, 4, 5]
>>> stack.append(6)
>>> stack.append(7)
>>> stack
[3, 4, 5, 6, 7]
>>> stack.pop()
7
>>> stack
[3, 4, 5, 6]
>>> stack.pop()
6
>>> stack.pop()
5
>>> stack
[3, 4]

>>> from collections import deque
>>> queue = deque(["Eric", "John", "Michael"])
>>> queue.append("Terry")           # Terry arrives
>>> queue.append("Graham")          # Graham arrives
>>> queue.popleft()                 # The first to arrive now leaves
'Eric'
>>> queue.popleft()                 # The second to arrive now leaves
'John'
>>> queue                           # Remaining queue in order of arrival
deque(['Michael', 'Terry', 'Graham'])

>>> vec = [2, 4, 6]
>>> [3*x for x in vec]
[6, 12, 18]

>>> [[x, x**2] for x in vec]
[[2, 4], [4, 16], [6, 36]]

>>> freshfruit = ['  banana', '  loganberry ', 'passion fruit  ']
>>> [weapon.strip() for weapon in freshfruit]
['banana', 'loganberry', 'passion fruit']

>>> [3*x for x in vec if x > 3]
[12, 18]
>>> [3*x for x in vec if x < 2]
[]

>>> vec1 = [2, 4, 6]
>>> vec2 = [4, 3, -9]
>>> [x*y for x in vec1 for y in vec2]
[8, 6, -18, 16, 12, -36, 24, 18, -54]
>>> [x+y for x in vec1 for y in vec2]
[6, 5, -7, 8, 7, -5, 10, 9, -3]
>>> [vec1[i]*vec2[i] for i in range(len(vec1))]
[8, 12, -54]

>>> [str(round(355/113, i)) for i in range(1, 6)]
['3.1', '3.14', '3.142', '3.1416', '3.14159']

>>> matrix = [
...     [1, 2, 3, 4],
...     [5, 6, 7, 8],
...     [9, 10, 11, 12],
... ]

>>> a = [-1, 1, 66.25, 333, 333, 1234.5]
>>> del a[0]
>>> a
[1, 66.25, 333, 333, 1234.5]
>>> del a[2:4]
>>> a
[1, 66.25, 1234.5]
>>> del a[:]
>>> a
[]

>>> del a

import module1[, module2[,... moduleN]

module1.函数名(参数列表) #调用函数

from modname import name1[, name2[, ... nameN]]
#from modname import * #导入所有函数变量等

name1(参数列表) #调用函数

#!/usr/bin/python3
# Filename: using_name.py

if __name__ == '__main__':
   print('程序自身在运行')
else:
   print('我来自另一模块')

>>> import fibo, sys
>>> dir(fibo)
['__name__', 'fib', 'fib2']
>>> dir(sys)  
['__displayhook__', '__doc__', '__excepthook__', '__loader__', '__name__',
 '__package__', '__stderr__', '__stdin__', '__stdout__',
 '_clear_type_cache', '_current_frames', '_debugmallocstats', '_getframe',
 '_home', '_mercurial', '_xoptions', 'abiflags', 'api_version', 'argv',
 'base_exec_prefix', 'base_prefix', 'builtin_module_names', 'byteorder',
 'call_tracing', 'callstats', 'copyright', 'displayhook',
 'dont_write_bytecode', 'exc_info', 'excepthook', 'exec_prefix',
 'executable', 'exit', 'flags', 'float_info', 'float_repr_style',
 'getcheckinterval', 'getdefaultencoding', 'getdlopenflags',
 'getfilesystemencoding', 'getobjects', 'getprofile', 'getrecursionlimit',
 'getrefcount', 'getsizeof', 'getswitchinterval', 'gettotalrefcount',
 'gettrace', 'hash_info', 'hexversion', 'implementation', 'int_info',
 'intern', 'maxsize', 'maxunicode', 'meta_path', 'modules', 'path',
 'path_hooks', 'path_importer_cache', 'platform', 'prefix', 'ps1',
 'setcheckinterval', 'setdlopenflags', 'setprofile', 'setrecursionlimit',
 'setswitchinterval', 'settrace', 'stderr', 'stdin', 'stdout',
 'thread_info', 'version', 'version_info', 'warnoptions']

 >>> a = [1, 2, 3, 4, 5]
>>> import fibo
>>> fib = fibo.fib
>>> dir() # 得到一个当前模块中定义的属性列表
['__builtins__', '__name__', 'a', 'fib', 'fibo', 'sys']
>>> a = 5 # 建立一个新的变量 'a'
>>> dir()
['__builtins__', '__doc__', '__name__', 'a', 'sys']
>>>
>>> del a # 删除变量名a
>>>
>>> dir()
['__builtins__', '__doc__', '__name__', 'sys']
>>>

这里给出了一种可能的包结构（在分层的文件系统中）:
sound/                          顶层包
      __init__.py               初始化 sound 包
      formats/                  文件格式转换子包
              __init__.py
              wavread.py
              wavwrite.py
              aiffread.py
              aiffwrite.py
              auread.py
              auwrite.py
              ...
      effects/                  声音效果子包
              __init__.py
              echo.py
              surround.py
              reverse.py
              ...
      filters/                  filters 子包
              __init__.py
              equalizer.py
              vocoder.py
              karaoke.py
              ...

import sound.effects.echo

sound.effects.echo.echofilter(input, output, delay=0.7, atten=4)

from sound.effects import echo

echo.echofilter(input, output, delay=0.7, atten=4)

from sound.effects.echo import echofilter

echofilter(input, output, delay=0.7, atten=4)

class Person:
    '''测试构造函数、类变量、成员变量、方法'''
    classVar='Person' #类变量
    __age = 0 #私有类变量

    def __init__(self,name): #构造方法
        self.name = name

    def __privateDoSth(self):
        print("私有方法")

    def sayHello(self):
        self.__privateDoSth()
        print("hello")

    
class Student(Person):
    '''测试继承、方法重写'''
    def sayHello(self):
        #self.__privateDoSth() #父类私有方法子类不能访问
        print("student")



#测试类变量
print(Person.classVar)
Person.classVar = 'PersonChange'
print(Person.classVar)
#私有变量
#print(Person.__age ) #报错

#初始化实例
p = Person('小明')
#调用方法
p.sayHello()
#调用私有方法
#p.__privateDoSth() #报错

s = Student('小华')
s.sayHello()

class Vector:
   def __init__(self, a, b):
      self.a = a
      self.b = b
 
   def __str__(self):
      return 'Vector (%d, %d)' % (self.a, self.b)
   
   def __add__(self,other):
      return Vector(self.a + other.a, self.b + other.b)
 
v1 = Vector(2,10)
v2 = Vector(5,-2)
print (v1 + v2)