大数据（7j）比较Python和Scala的yield

Posted 2021-05-24 小基基o_O

以Python为参照速查Scala语法

• 简单的yield
• yield+判断

简单的yield

Python的yield在函数中，遍历函数取值

def f():
    for i in range(5):
        yield i ** 2

Scala的yield配合for用来赋值

val vector = for (i <- 1 to 5) yield {
  i * i
}

print(vector)  // Vector(1, 4, 9, 16, 25)

yield+判断

Python：

def f():
    for i in range(10):
        if i % 2 == 1:
            yield i ** 2

Scala：if在循环体内，会yield出()

val vector = for (i <- 1 to 10) yield {
  if (i % 2 == 1) {
    i * i
  }
}

print(vector) // Vector(1, (), 9, (), 25, (), 49, (), 81, ())

Scala：if在条件内，才不会yield出()

val vector = for (i <- 1 to 10 if i % 2 == 1) yield {
  i * i
}

print(vector) // Vector(1, 9, 25, 49, 81)