Python和Scala的语法对照表(持续更新中)

Lambda

	Python	Scala
传入多个参数	a = lambda x,y,z:(x+8)*y-z print(a(5,6,8))
lambda表达式后面传参	(lambda x, y: x if x>y else y)(1, 2)
lambda函数本身做为return的值	def add(n):     return lambda x: x+n f = add(1) print(f(2))
列表结合使用	L = [lambda x: x**2,\      lambda x: x**3,\      lambda x: x**4] for x in L:         print(x(2)) print("------------------------------") print(L[0](2))
字典配合使用	key = 'B' dic = { 'A': lambda: 2*2,\         'B': lambda: 2*4,\         'C': lambda: 2*6} print(dic[key]())
结合map函数使用	squares = map(lambda x: x**2, range(5)) print(list(squares))
结合reduce函数使用	from functools import reduce def add(x, y) : # 两数相加     return x + y print(reduce(add, [1,2,3,4,5])) print(reduce(lambda x, y: x+y, [1,2,3,4,5]))
结合filter函数使用	print(list(filter(lambda x: x%2==0,  [1,2,3,4,5,6])))
结合sorted函数使用	info = [('James',32), ('Alies',20), ('Wendy',25)] print(sorted(info, key=lambda age:age[1]))# 按照第二个元素，索引为1排序
要点	①lambda 函数不能包含命令， ②包含的表达式不能超过一个。 ③lambda 并不会带来程序运行效率的提高，只会使代码更简洁。

List

	Python	Scala
空List	a = []	val a = List() //List[Nothing]
Int	a = [1,2,3,4,5]	val a = List(1,2,3,4,5)
String	a = ["a", "b"]	val a: List[String] = List("Hello", "World")
不同类型	a = [1,"Hello"]	val a = List(1, "Hello") //List[Any]
2维	a = [[1,2,3], [4,5,6]]	val a = List(List(1,2,3), List(4,5,6))
索引	a[10]	a(10)
截取	a[0:2]	a.slice(0,2)
是否为空	not a a==[] len(a)==0	a.isEmpty
append	a.append(6)	a :+ 6
连接	a.extend([4,5,6])	List.concat(List(1,2,3), List(4,5,6))
反转	a[::-1]	a.reverse

HashMap

	Python	Scala
新建	map = {"one": 1, "two":2}	val map = Map("one"->1, "two"->2)
新建		val map = Map(("one", 1), ("two", 2))
获取	map["one"]	map("one")
包含	"one" in map	map.contains("one")
添加	map["three"] = 3	map + ("three"->3)
删除	del map["three"]	map - "three"
keys	map.keys()	map.keys
values	map.values()	map.values
concat	map1.update(map2)	map1 ++ map2

Set

	Python	Scala
新建	s = {1,2,3}	val s = Set(1,2,3)
新建	s = set([1,2,3])
添加	s.add(4)	s + 4
删除	s.remove(4)	s - 4
是否为空	nor s	s.isEmpty
min	min(s)	s.min
max	max(s)	s.max
concat	s1.union(s2)	s1.union(s2)
concat		s1 ++ s2

For loop

	Python	Scala
Range	for x in range(5): print(x)	for(x <- Range(1, 5)) println(x)
List	for x in li: print(x)	for (x <- li) println(x)
Map	for k, v in map1.items(): print(k,v)	for ((k,v) <- map1) println(k, v)

Range

Python	Scala
range(1, 10) (inclusive, exclusive)	Range(1, 10) (inclusive, exclusive)
	1 to 10 (inclusive, inclusive)
	1 until 10 (inclusive, exclusive)
range(10) (exclusive)
range(1, 10, 2)	1 to 10 by 2
仅支持int	1.0 to 10.0 by 0.5
仅支持int	'a' to 'g' by 2

列表推导式

Python	Scala
dogBreeds =["Doberman", "Yorkshire Terrier", "Dachshund","Scottish Terrier", "Great Dane","Portuguese Water Dog"] filteredBreeds=[breed for breed in dogBreeds if "Terrier" in breed and not breed.startswith('Yorkshire')] print(filteredBreeds)	val dogBreeds = List("Doberman", "Yorkshire Terrier", "Dachshund","Scottish Terrier", "Great Dane","Portuguese Water Dog") val filteredBreeds = for {breed <- dogBreeds if breed.contains("Terrier") && !breed.startsWith("Yorkshire")} yield breed println(filteredBreeds)

Main函数写法

Python	Scala
def main():     print("hello world") if __name__ == '__main__':     main()	object HelloWorld{ def main(args : Array[String]){ println("HelloWorld") } }

迭代器

Python	Scala
import sys         # 引入 sys 模块 list=["Baidu", "Google", "Runoob", "Taobao"] it = iter(list)    # 创建迭代器对象   while True:     try:         print (next(it))     except StopIteration:	object Test {    def main(args: Array[String]) {       val it = Iterator("Baidu", "Google", "Runoob", "Taobao")              while (it.hasNext){          println(it.next())       }    } }

生成器

Reference:
[1]给Python程序员的Scala入门教程

[2]Scala学习日志（三）——轻便神奇的for推导式

[3]python中lambda的用法

[4]Scala编程 Lambda Expressions

[5]scala中的Lambda表达式