- 列表[List] 元组(truple) 字典{dict}
# 列表中的每个元素都分配一个数字 - 它的位置，或索引，第一个索引是0，第二个索引是1，依此类推# list comprehension[i for i in range(10)]# 元组与列表类似，不同之处在于元组的元素不能修改# truple generator(i for i in range(10))# 字典的每个键值 key=>value 对用冒号 : 分割，每个键值对之间用逗号 , 分割，整个字典包括在花括号 {} 中# dict comprehension{k:1 for k in range(10)} - 生成器（generator） 带有 yield 的函数在 Python 中被称之为 generator（生成器）
def my_range(n): i = 0 while i != n: i += 1 yield ir = my_range(10)for i in r: print(i)
- 迭代器 iterator
- 迭代器是访问集合元素的一种方式。迭代器对象从集合的第一个元素开始访问，直到所有的元素被访问完结束。迭代器只能往前不会后退
while True: try: i = next(iter_obj) except StopIteration: breakclass Pow2(object): def __init__(self, max): self.max = max self.n = 0 def __iter__(self): self.n = 0 return self def __next__(self): if self.n < self.max: self.n += 1 return 2 ** self.n else: raise StopIterationp = Pow2(10)for i in p: print(i)
- 实例方法(instance method), 类方法(class method), 静态方法(static method)
# instance method a = A() a.foo() a.bar()# class method bind class# static methodclass A(object): @staticmethod def s_foo(): pass @classmethod def c_foo(cls): pass def foo(self): passa = A()a.foo()A.c_foo()
- 深拷贝 浅拷贝
# 深拷贝from copy import deepcopyl1 = []l2 = deepcopy(l1)l1.append(1)print(l2)# 浅拷贝l1 = [1, [1, 2], 3]l2 = l1[:]def foo(a=[]): a.append(1) print(a)foo()foo()
- lambda表达式, 闭包(closure)
- lambda
import functools import operator mul2 = lambda x: 2 * x print(mul2(3)) print(list(map(lambda x: 3 * x, [1, 2, 3, 4]))) print(list(filter(lambda x: x % 3 == 0, [1, 2, 3, 4]))) print(functools.reduce(operator.add, [1, 2, 3, 4, 5], 5))
- closure
# 例子一 def greeting(msg): def hello(name): print(msg, name) return hello h = greeting("welcome") h("akira") # 例子二 l = [] for i in range(10): def _(i=i): print(i) l.append(_) for f in l: f() - *args, **kwargs args获取tuple, kwargs获取kwargs
def log(*args, **kwargs): print("args", args) print("kwargs", kwargs)log(1, 2, 3, 4)log(1, 2, [1, 2, 3], c=4) - 递推式构造列表
# list comprehensionr1 = [i for i in range(10)]print(r1)# dict comprehensionr2 = {k:1 for k in range(10)}print(r2)# list generatorr3 = (i for i in range(10))print(list(r3)) - 装饰器(decorator) 可用于AOP(aspect oriential programming) 例如:
if debug: xxxelse: yyy
decorator例子
def simple_wrapper(fn): def _(): #print(fn.__name__) return fn() return _def fix_arg_wrapper(fn): def _(x): #print(fn.__name__) return fn(x) return _def all_args_wrapper(fn): def _(*args, **kwargs): print(*args, **kwargs) return fn(*args, **kwargs) return _@simple_wrapperdef foo(): pass@all_args_wrapperdef bar(a, b, c): passfoo()bar(1, 2, 3)
- 魔法方法(magic method)
形如:
__xxx__ 例子:
class LogAll(object): def __init__(self): self.a = 1 self.b = 2 self.c = 3 def __getattribute__(self, item): print(item)l = LogAll()print(l.a)l.a = 1l.bl.cclass Any(object): def __getattr__(self, item): print(item) def __setattr__(self, key, value): print("set", key, value)a = Any()a.aa.a = 1class Any2(object): def __getattr__(self, item): def _(*args, **kwargs): print("function name", item) print("args", args) print("kwargs", kwargs) setattr(self, item, _) return _a = Any2()a.a1(1, 2, 3)a.a2(1, 2, [1, 2, 3], c=[]) - Mixin模式 例子：
class A(object): def foo(self): print("foo") def bar(self): print("bar") self.shit()class B(object): def shit(self): print("shit")class C(A, B): passc = C()c.bar() - 字符串反转
new_x = str_x[::-1]
- 关于i++ python 中的没有 i++ ，如果写了会报语法错误。 但是python 中有 --i,++i,+-i,-+i,他们不是实现-1操作的，仅仅是作为判断运算符号,类似数学中的负负得正
i = 2print ++i //2print -+i //-2print +-i //-2print --i //2
逻辑表达式
python 中没有 && ，!, || 这3个运算符，在逻辑表达式中写成这3个会抱逻辑错误的。要实现同样的功能，要写成 and，not，or 返回值 2 and 3 返回3 返回值 2 or 3 返回2 返回值 not 2 and 3 返回 False- if-elif-else的写法 例如：比较两个二叉树是否相同
class TreeNode: def __init__(self, x): self.val = x self.left = None self.right = Noneclass Solution: def isSameTree(self, p: 'TreeNode', q: 'TreeNode') -> 'bool': if p is None and q is None: return True elif p is not None and q is not None: if p.val == q.val: return self.isSameTree(p.left, q.left) and self.isSameTree(p.right, q.right) else: return False else: return False
- 其它
top_element = stack.pop() if stack else '#'
相当于
if stack: top_element = stack.pop()else: top_element = '#'