Python优化代码的技巧分享

def get_user(user):
    # 常规代码
    if user:
        return user
    return "匿名用户"
# 短路来简写代码
def get_user(user):
    return user or "匿名用户"

# 使用循环
def reverse(lst):
    new_lst = []
    for i in range(len(lst) - 1, -1, -1):
        new_lst.append(lst[i])
    return new_lst
lst = [1, 2, 3, 4, 5]
print(reverse(lst)) # [5, 4, 3, 2, 1]
# 使用切片
def reverse(lst):
    return lst[::-1]
lst = [1, 2, 3, 4, 5]
print(reverse(lst)) # [5, 4, 3, 2, 1]

# 使用普通的循环
lst = [1, 2, 3, 4, 5, 6]
new_lst = []
for x in lst:
    if x % 2 == 0:
        new_lst.append(x * 2)
print(new_lst) # [4, 8, 12]

# 使用列表推导式
lst = [1, 2, 3, 4, 5, 6]
new_lst = [x * 2 for x in lst if x % 2 == 0]
print(new_lst) # [4, 8, 12]

# 使用普通的循环
lst = [1, 2, 3, 4, 5, 6]
sum = 0
for x in lst:
    if x % 2 == 0:
        sum += x ** 2
print(sum) # 56

# 使用生成器表达式
lst = [1, 2, 3, 4, 5, 6]
sum = sum(x ** 2 for x in lst if x % 2 == 0)
print(sum) # 56

# 使用普通的循环
lst = ["a", "b", "c", "d", "e"]
index = 0
for x in lst:
    print(index, x)
    index += 1
# 输出：
# 0 a
# 1 b
# 2 c
# 3 d
# 4 e

# 使用枚举
lst = ["a", "b", "c", "d", "e"]
for index, x in enumerate(lst):
    print(index, x)
# 输出：
# 0 a
# 1 b
# 2 c
# 3 d
# 4 e

# 使用普通的if-else语句
num = -5
if num > 0:
    sign = "positive"
else:
    sign = "negative"
print(sign) # negative

# 使用三元运算符
num = -5
sign = "positive" if num > 0 else "negative"
print(sign) # negative

# 使用多个if-elif-else语句
def foo(x):
    if x == "a":
        return 1
    elif x == "b":
        return 2
    elif x == "c":
        return 3
    else:
        return -1
print(foo("a")) # 1
print(foo("d")) # -1
# 使用字典
def foo(x):
    dic = {"a": 1, "b": 2, "c": 3}
    return dic.get(x, -1)
print(foo("a")) # 1
print(foo("d")) # -1

# 使用普通的函数调用
import time
def foo():
    # do something
    time.sleep(1)
start = time.time()
foo()
end = time.time()
print(f"foo() took {end - start} seconds to run.") 

# 使用装饰器
import time
def timer(func):
    def wrapper(*args, **kwargs):
        start = time.time()
        result = func(*args, **kwargs)
        end = time.time()
        print(f"{func.__name__}() took {end - start} seconds to run.")
        return result
    return wrapper
@timer # 相当于 foo = timer(foo)
def foo():
    # do something
    time.sleep(1)
foo() 

# 使用普通的try-finally语句
file = open("test.txt", "r")
try:
    content = file.read()
    print(content)
finally:
    file.close()

# 使用上下文管理器
with open("test.txt", "r") as file:
    content = file.read()
    print(content)

lst = [9,2,3,4,5,5,1,2,3]
# 不使用lambda表达式
def add(item):
   return item
print(sorted(add, item))
# 使用lambda表达式
print(sorted(lst, key=lambda x:x))

# 不使用map函数
lst = ["1", "2", "3", "4", "5"]
new_lst = []
for x in lst:
    new_lst.append(int(x))
print(new_lst) # [1, 2, 3, 4, 5]
# 使用map函数
lst = ["1", "2", "3", "4", "5"]
new_lst = list(map(int, lst))
print(new_lst) # [1, 2, 3, 4, 5]

# 不使用filter函数
lst = [1, 2, 3, 4, 5]
new_lst = []
for x in lst:
    if x % 2 == 0:
        new_lst.append(x)
print(new_lst) # [2, 4]
# 使用filter函数
lst = [1, 2, 3, 4, 5]
new_lst = list(filter(lambda x: x % 2 == 0, lst))
print(new_lst) # [2, 4]

# 不使用@property装饰器
class Person:
   def __init__(self, name, age):
       self.name = name
       self.age = age
   def get_name(self):
       return self.name
   def set_name(self, name):
       if not isinstance(name, str):
           raise TypeError("name must be a string")
       self.name = name
   def get_age(self):
       return self.age
   def set_age(self, age):
       if not isinstance(age, int):
           raise TypeError("age must be an integer")
       if age < 0 or age > 150:
           raise ValueError("age must be between 0 and 150")
       self.age = age
p = Person("kira", 40) # 实例化
print(p.get_name()) # kira
print(p.get_age()) # 40
p.set_name("勇哥")
p.set_age(35)
print(p.get_name()) # 勇哥
print(p.get_age()) # 35
# 使用@property装饰器
class Person:
   def __init__(self, name, age):
       self._name = name
       self._age = age
   @property
   def name(self):
       return self._name
   @name.setter
   def name(self, name):
       if not isinstance(name, str):
           raise TypeError("name must be a string")
       self._name = name
   @property
   def age(self):
       return self._age
   @age.setter
   def age(self, age):
       if not isinstance(age, int):
           raise TypeError("age must be an integer")
       if age < 0 or age > 150:
           raise ValueError("age must be between 0 and 150")
       self._age = age
p = Person("kira", 30)
print(p.name) # kira
print(p.age) # 30
p.name = "勇哥"
p.age = 35
print(p.name) # 勇哥
print(p.age) # 35

# 不使用__slots__属性
class Person:
   def __init__(self, name, age):
       self.name = name
       self.age = age
p = Person("勇哥", 90)
print(p.__dict__) 
print(p.__sizeof__()) 

# 使用__slots__属性
class Person:
    # 指定该类只能拥有name和age两个属性
    __slots__ = ("name", "age")
    def __init__(self, name, age):
        self.name = name
        self.age = age
p = Person("Alice", 20)
print(p.__sizeof__()) 
print(p.__dict__)