python总结知识点

 python类构造函数作为另个函数的__init__参数。

class MyOdlHttp():
  # username = ''
  # password = ''
 
  def __init__(self, username, password):
    self.haha = username
    self.passw = password
    print(username)
    print(self.haha)
 
my_old_http = MyOdlHttp('admin', '123')
print(my_old_http)
print(my_old_http.haha)
print(my_old_http.passw)
print('=====================')



class Test():
  def __init__(self,input):
    self.output = MyOdlHttp('admin', '123')
aa = Test('ass').output
print(aa.haha)
print(aa.passw)  
#out = Test(MyOdlHttp('admin','123'))
print('=====================')



admin
admin
<__main__.MyOdlHttp object at 0x7fd1ea3f9350>
admin
123
=====================
admin
admin
admin
123
=====================

python delete()

motorcycles = ['honda', 'yamaha', 'suzuki']
print(motorcycles)

del motorcycles[0]
print(motorcycles)

['honda', 'yamaha', 'suzuki']
['yamaha', 'suzuki']

python setattr()函数

class Person:
  name = "John"
  age = 36
  country = "Norway"

setattr(Person, 'age', 40)
print(Person.age)
print(Person().age)

40
40

class Config():
  a = 1
  b = 2
print(Config.a)
print(Config().a)

1
1

python assert()

#price 为原价，discount 为折扣力度
def apply_discount(price, discount):
    updated_price = price * (1 - discount)
    #assert 0 <= updated_price <= price, '折扣价应在 0 和原价之间'
    assert 0 <= updated_price <= price
    return updated_price
print(apply_discount(100,0.2))
print(apply_discount(100,1.1))

80.0
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-29-bf98d6e6aa6b> in <module>()
      6     return updated_price
      7 print(apply_discount(100,0.2))
----> 8 print(apply_discount(100,1.1))

<ipython-input-29-bf98d6e6aa6b> in apply_discount(price, discount)
      3     updated_price = price * (1 - discount)
      4     #assert 0 <= updated_price <= price, '折扣价应在 0 和原价之间'
----> 5     assert 0 <= updated_price <= price
      6     return updated_price
      7 print(apply_discount(100,0.2))

AssertionError: 

print(1)
assert 1 == 2
print(2)

1
---------------------------------------------------------------------------
AssertionError                            Traceback (most recent call last)
<ipython-input-30-ca408cea71f3> in <module>()
      1 print(1)
----> 2 assert 1 == 2
      3 print(2)

AssertionError: 

python arg、*args、**kwargs

def function(arg,*args,**kwargs):
    print(arg,args,kwargs)

function(6,7,8,9,a=1, b=2, c=3)

6 (7, 8, 9) {'a': 1, 'b': 2, 'c': 3}

关于类：

class PredictGlaucoma():
    """主控制程序"""

    def __init__(self, args):
        self.a = args


    def initial_disc(self, args):
        # disc params
        da = 8
        self.dp = da
        self.out = 9
p = PredictGlaucoma('2')
print(p.a)
print(p.initial_disc('3'))
print(p.dp)
print(p.out)


2
None
8
9

>>>class A(object):
...     bar = 1
... 
>>> a = A()
>>> getattr(a, 'bar')          # 获取属性 bar 值
1
>>> setattr(a, 'bar', 5)       # 设置属性 bar 值
>>> a.bar
5


>>>class A():
...     name = "runoob"
... 
>>> a = A()
>>> setattr(a, "age", 28)
>>> print(a.age)
28
>>>

class EllipseParams():
    """椭圆相关参数（用于视盘和视杯）"""

    def __init__(self, mode) -> None:
        self.mode = mode
        self.status = -1  # 状态位
        self.dic_status = None  # 状态位之间，描述与数值间的映射
        # self.initial_to_blank()
        # self.thickness = (1 if self.mode == 'test'
        #                   else int(cfg_disc['thickness']))
        # self.is_visible = False  # 是否检测出视盘（或视杯）
        # self.model = None
        # self.pred_path = None  # 视盘（或视杯）的预测图路径
        # self.gray_path = None  # 视盘（或视杯）的灰度图路径
        # self.path_miss = None  # 未检测到视盘或视杯时的记录文件
        # self.lr_mismatch = False  # 算法推理的左右眼是否与提供的一致
        # self.dir_mid = None  # 中间结果的保存目录
        # self.dir_final = None  # 最终结果的保存目录
        # self.thresh_pred = -1
        # self.disc_outside_fundus = False

    def initial_to_blank(self):
        # center(x,y), size(w,h), angle
        # self.params_512 = ((-1, -1), (-1, -1), -1)
        self.center_512 = (-1, -1)  # 512尺寸图像上的椭圆中心
        self.angle = -1  # 椭圆旋转角度
        self.size_512_pixel = (-1, -1)  # 椭圆直径，单位为像素, size[0]<size[1]
        self.is_width_gt_height = False  # 是否宽度大于高度（即横向椭圆）
        self.width_roi = -1  # roi(视盘或视杯)的宽度
        self.height_roi = -1  # roi的高度
        self.size_512_mm: Tuple[float, float] = (-1, -1)  # 椭圆直径，单位为毫米, (w, h)
        self.area = [-1, -1, -1]  # area_mm, area_pixel, area_ratio
        self.curvature = (-1, -1)  # 曲率
        self.color_contrast = -1  # 颜色对比度（内比外）

test = EllipseParams('12')
test.initial_to_blank()
print(test.status)
print(test.angle)
print(test.initial_to_blank().angle)



-1
-1
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-11-5125d31ef93f> in <module>()
     38 print(test.status)
     39 print(test.angle)
---> 40 print(test.initial_to_blank().angle)

AttributeError: 'NoneType' object has no attribute 'angle'

hasattr() 函数用于判断对象是否包含对应的属性。

class CLanguage:
    '''这是一个学习Python定义的一个类'''
    def __init__(self,name,add):
        self.a = name
        self.b = add
        print(name,"的网址为:",add)
#创建 add 对象，并传递参数给构造函数
add = CLanguage("C语言中文网","http://c.biancheng.net")
print(add.a)
print(add.b)
print(CLanguage('a','b').a)

C语言中文网 的网址为: http://c.biancheng.net
C语言中文网
http://c.biancheng.net
a 的网址为: b
a

python __call__()方法

class CLanguage:
    # 定义__call__方法
    def __call__(self,name,add):
        print("调用__call__()方法",name,add)
        return 'nihao'
clangs = CLanguage()
c = clangs("C语言中文网","http://c.biancheng.net")
print(c)
print('===============')
clangs("C语言中文网","http://c.biancheng.net")



调用__call__()方法 C语言中文网 http://c.biancheng.net
nihao
===============
调用__call__()方法 C语言中文网 http://c.biancheng.net
nihao

class A():
    def m(self):
        print('a')
    def n(self):
        print('b')

a = A()
a.m()

a


# 使用__call__后
class A():
    def __call__(self):
        print('a')
    def n(self):
        print('b')

a = A()
a()

a

python __getitem__()

class DataTest:
    def __init__(self,id,address):
        self.id=id
        self.address=address
        self.d={self.id:1,
                self.address:"192.168.1.1"
                }
        
    def __getitem__(self,key):
        return "hello"
    
 
data=DataTest(1,"192.168.2.11")
print(data)
print(type(data))
print (data[11000])


<__main__.DataTest object at 0x7fc227f1da90>
<class '__main__.DataTest'>
hello

在用 for..in.. 迭代对象时，如果对象没有实现 __iter__ __next__ 迭代器协议，Python的解释器就会去寻找__getitem__ 来迭代对象，如果连__getitem__ 都没有定义，这解释器就会报对象不是迭代器的错误：

TypeError: 'Animal' object is not iterable

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class Animal:
    def __init__(self, animal_list):
        self.animals_name = animal_list
      
    def __getitem__(self, index):
      return self.animals_name[index]

animals = Animal(["dog","cat","fish"])
for animal in animals:
    print(animal)


dog
cat
fish

class Tag:
    def __init__(self,id):
        self.id=id
 
    def __getitem__(self, item):
        print('这个方法被调用')
        return self.id
 
a=Tag('This is id')
print(a.id)
out = print(a[1681])
print(out)


This is id
这个方法被调用
This is id
None

class Tag:
    def __init__(self):
        self.change={'python':'This is python'}
 
    def __getitem__(self, item):
        print('这个方法被调用')
        return self.change[item]
 
a=Tag()
print(a.change)
print(a['python'])


{'python': 'This is python'}
这个方法被调用
This is python

python __len__()方法：

class Employee:
    #name = ''
 
    def __init__(self, n):
        self.name = n
        print(self.name)
        print(n)
        print('=============')
 
    def __len__(self):
        print(self.name)
        return len(self.name)
 
 
e = Employee('Pankaj')
 
print('employee object length =', len(e))

Pankaj
Pankaj
=============
Pankaj
employee object length = 6

class CountList:
  def __init__(self, *args):
    self.values = [x for x in args]
    self.count = {}.fromkeys(range(len(self.values)),0)
  def __len__(self):
    return len(self.values)
  def __getitem__(self, key):
    self.count[key] += 1
    print(self.count[key])
    return self.values[key]

c1 = CountList(1,3,5,7,9)
print(c1.values)
print(c1.count)
print(len(c1))
print(len(c1.values))
print(len(c1.count))
print('=========================')
print(c1[3])
print(c1[2])


[1, 3, 5, 7, 9]
{0: 0, 1: 0, 2: 0, 3: 0, 4: 0}
5
5
5
=========================
1
7
1
5