类变量 类方法 和 静态方法
"""
类变量 类方法 和 静态方法
https://www.perry.qa/morse
"""
class Student:
student_count = 0 # 类变量
def __init__(self, name):
self.name = name
Student.student_count += 1
@classmethod # 类方法
def add_count(cls, count):
cls.student_count += count
@classmethod
def get_count(cls):
return cls.student_count
@classmethod
def build(cls, str):
return cls(str.split(" ")[0])
@staticmethod # 静态方法
def build_stu(name):
return Student(name)
if __name__ == '__main__':
p = Student("morningcat")
print("student count:{}".format(Student.student_count))
Student.add_count(100)
print("student count:{}".format(Student.get_count()))
p = Student.build("Hello world")
print(p.name)
魔法方法
"""
魔法方法:特殊方法
通常写在类定义里,用来定义类如何与内置函数和运算符交互
更多魔法方法:https://diveintopython3.net/special-method-names.html
"""
class Order:
def __init__(self, count):
self.count = count
def __add__(self, other):
return Order(self.count + other.count)
def __str__(self):
return "Order({})".format(self.count)
def __len__(self):
return self.count
def __call__(self, add_count):
self.count += add_count
if __name__ == '__main__':
# 同等效果
x1 = 1 + 2
x2 = (x := 1).__add__(2)
# 自定义类
a = Order(12)
b = Order(25)
order_c = a + b
print(order_c)
order_c(100)
print(order_c)
可迭代对象
"""
可迭代对象, 以及迭代器
"""
class LineIterator:
def __init__(self, filepath):
self.file = open(filepath, 'r')
def __iter__(self):
return self
def __next__(self):
line = self.file.readline()
if line:
return line
else:
self.file.close()
raise StopIteration("file read over")
if __name__ == '__main__':
# 常见可迭代对象
s1 = "hello"
print(hasattr(s1, "__iter__"))
for x in s1:
print(x)
l1 = [1, 2, 3]
print(hasattr(l1, "__iter__"))
for x in l1:
print(x)
num1 = 133
print(hasattr(num1, "__iter__"))
# 模拟迭代原理
it = iter(l1)
while True:
try:
print(next(it))
except StopIteration:
break
fileIter = LineIterator("/home/1.txt")
for line in fileIter:
print(line)
推导式
"""
推导式: 可高效获取可迭代对象(list dict set)
"""
if __name__ == '__main__':
# 列表推导式
list1 = range(11)
list2 = [x ** 2 for x in list1 if x % 2 == 0]
print(list2)
letters = ['a', 'b', 'c']
nums = [1, 2, 3]
list3 = [(i, j) for i in letters for j in nums]
print(list3)
# 字典推导式
dict1 = {i: j for i, j in zip(letters, nums)}
print(dict1)
# 集合推导式
set1 = {x for x in letters}
print(set1 )
生成器
"""
生成器
"""
def square_numbers(nums):
"""
包含yield关键字,即是一个生成器函数
"""
for i in nums:
yield i ** 2
if __name__ == '__main__':
gen = square_numbers(range(5))
print(gen)
print(next(gen))
for x in gen:
print(x)
# 生成器
gen2 = (x ** 2 for x in range(5))
print(gen2)
装饰器
"""
装饰器
"""
import functools
import time
def timer(threshold):
def decorator(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
start = time.time()
result = func(*args, **kwargs)
end = time.time()
if end - start > threshold:
raise Exception(f"timeout {end - start}")
return result
return wrapper
return decorator
@timer(0.1) # 0.1 second
def test1():
time.sleep(0.4)
if __name__ == '__main__':
test1()
lambda函数
"""
匿名函数 : lambda函数
"""
def user_login(user):
level_credit_dict = {
1: lambda x: x + 2,
2: lambda x: x + 5,
3: lambda x: x + 10,
}
user.credit = level_credit_dict[user.level](user.credit)
if __name__ == '__main__':
add = lambda a, b: a + b
print(add(1, 3))
list1 = [1, 2, 3, 4, 5]
list2 = list(map(lambda x: x ** 2, list1))
print(list2)
