python和js 相同之处 Python 和 JS 有哪些相同之处

int('3') # 3
str(3.14) # '3.14'
float('3.14') # 3.14
# 区别于 JS 只有 Number 一种类型，Python 中数字中的不同类型也能相互强制转换
float(3) # 3.0
bool(3) # True
bool(0) # False

1 + 1.0 # 2.0
1 + False # 1
1.0 + True # 2.0
# 区别于 JS 的 String + Number = String, py 中 str + int 会报错
1 + '1' # TypeError: cannot concatenate 'str' and 'int' objects

type(1.3) == float # True
isinstance('a', str) # True
isinstance(1.3, int) # False
isinstance(True, bool) # True
isinstance([], list) # True
isinstance({}, dict) # True

L = [1, 2, 3]
print L[-1] # '3'
L.append(4) # 末尾添加元素
print L # [1, 2, 3, 4]
L.insert(0, 'hi') # 指定索引位置添加元素
print L # ['hi', 1, 2, 3, 4]
L.pop() # 末尾移除元素 L.pop(2) ?????? 2 ???
print L # ['hi', 1, 2, 3]

t = (1, 2, 3)
print t[0] # 1
t[0] = 11 # TypeError: 'tuple' object does not support item assignment
t = (1)
print t # 1 t 的结果是整数 1
t = (1,) # 为了避免出现如上有歧义的单元素 tuple，所以 Python 规定，单元素 tuple 要多加一个逗号","
print t # (1,)

d = {
  'a': 1,
  'b': 2,
  'c': 3
}

# 遍历 dict
for key,value in d.items():
  print('%s: %s' % (key,value))
# a: 1
# c: 3
# b: 2

s = set(['A', 'B', 'C', 'C'])
print s # set(['A', 'C', 'B'])
s.add('D')
print s # set(['A', 'C', 'B', 'D'])
s.remove('D')
print s # set(['A', 'C', 'B'])

L = ['apple', 'banana', 'orange']
for index, name in enumerate(L): # enumerate() 函数把 ['apple', 'banana', 'orange'] 变成了类似 [(0, 'apple), (1, 'banana'), (2, 'orange')] 的形式
  print index, '-', name
# 0 - apple
# 1 - banana
# 2 - orange

d = { 'apple': 6, 'banana': 8, 'orange': 5 }
print d.values() # [6, 8, 5]
for v in d.values()
  print v
# 6
# 8
# 5

d = { 'apple': 6, 'banana': 8, 'orange': 5 }
for key, value in d.items()
  print key, ':', value
# apple : 6
# banana: 8
# orange: 5

L = ['apple', 'banana', 'orange', 'pear']
L[0:2] # ['apple', 'banana'] 取前 2 个元素
L[:2] # ['apple', 'banana'] 如果第一个索引是 0，可以省略
L[:] # ['apple', 'banana', 'orange', 'pear'] 只用一个 : ，表示从头到尾
L[::2] # ['apple', 'orange'] 第三个参数表示每 N 个取一个，这里表示从头开始，每 2 个元素取出一个来

L = []
for x in range(1, 11):
  L.append(x * x)

def greet(name='World'):
  print 'Hello, ' + name + '.'
greet() # Hello, World.
greet('Python') # Hello, Python.

def fn(*args):
  print args
fn() # ()
fn('a') # ('a',)
fn('a', 'b') # ('a', 'b')

def f(x):
  return x * x
print map(f, [1, 2, 3, 4, 5, 6, 7, 8, 9]) # [1, 4, 9, 16, 25, 36, 49, 64, 81]

def f(x, y):
  return x * y
reduce(f, [1, 3, 5]) # 15

def is_odd(x):
  return x % 2 == 1
filter(is_odd, [1, 4, 6, 7, 9, 12, 17]) # [1, 7, 9, 17]

map(lambda x: x * x, [1, 2, 3, 4, 5, 6, 7, 8, 9]) # [1, 4, 9, 16, 25, 36, 49, 64, 81]

def f(x):
  return x * x

# 希望一次返回3个函数，分别计算1x1,2x2,3x3:
def count():
  fs = []
  for i in range(1, 4):
    def f():
      return i * i
    fs.append(f)
  return fs
f1, f2, f3 = count() # 这种写法相当于 ES6 中的解构赋值
print f1(), f2(), f3() # 9 9 9

def count():
  fs = []
  for i in range(1, 4):
    def f(j):
      def g(): # 方法一
        return j * j
      return g
    r = f(i)
    fs.append(r)
  return fs
f1, f2, f3 = count()
print f1(), f2(), f3() # 1 4 9

def count():
  fs = []
  for i in range(1, 4):
    def f(j = i): # 方法二
      return j * j
    fs.append(f)
  return fs
f1, f2, f3 = count()
print f1(), f2(), f3() # 1 4 9

@Post('/rider/detail') // URL 路由
@log()         // 打印日志
 @ResponseBody
 public async getRiderBasicInfo(
  @RequestBody('riderId') riderId: number,
  @RequestBody('cityId') cityId: number,
 ) {
  const result = await this.riderManager.findDetail(cityId, riderId)
  return result
 }

# 我们想把调用的函数名字给打印出来
@log()
def factorial(n):
  return reduce(lambda x,y: x*y, range(1, n+1))
print factorial(10)
# 来看看 @log() 的定义
def log():
  def log_decorator(f):
    def fn(x):
      print '调用了函数' + f.__name__ + '()'
      return f(x)
    return fn
  return log_decorator
# 结果
# 调用了函数 factorial()
# 3628800
class

class Person {
  constructor(name, age) {
    this.name = name
    this.age = age
  }
}
const child1 = new Person('Xiao Ming', 10)

# 定义一个 Person 类：根据 Person 类就可以造成很多 child 实例
class Person(object):
  address = 'Earth' # 类属性 (实例公有)
  def __init__(self, name, age): # 创建实例时，__init__()方法被自动调用
    self.name = name
    self.age = age
  def get_age(self): # 定义实例方法，它的第一个参数永远是 self，指向调用该方法的实例本身，其他参数和普通函数是一样的
    return self.age
child1 = Person('Xiao Ming', 10)
child2 = Person('Xiao Hong', 9)
print child1.name # 'Xiao Ming'
print child2.get_age() # 9
print child1.address # 'Earth'
print child2.address # 'Earth'

class Person(object):
  def __init__(self, name, age):
    self.name = name
    self.age = age
class Student(Person):
  def __init__(self, name, age, grade):
    super(Student, self).__init__(name, age) # 这里也能写出 Person.__init__(self, name, age)
    self.grade = grade
s = Student('Xiao Ming', 10, 90)
print s.name # 'Xiao Ming'
print s.grade # 90

isinstance(s, Person)
isinstance(s, Student)