从列表中过滤-Python

Question

I was wondering if someone can help me with a homework problem.

Write a function, func(a,x), that takes an array, a, x being both numbers, and returns an array containing only the values of a that are greater than or equal to x

I have

def threshold(a,x):
    for i in a:
        if i>x: print i

But this is the wrong method as I'm not returning it as an array. Can someone hint me the right direction. Thanks a lot in advance

Answer 1

使用清单理解 ：

[i for i in a if i>x]

Answer 2

use the in-built function filter() :

In [59]: lis=[1,2,3,4,5,6,7]
In [61]: filter(lambda x:x>=3,lis)  #return only those values which are >=3
Out[61]: [3, 4, 5, 6, 7]

Answer 3

You could use a list comprehension :

def threshold(a, x):
    return [i for i in a if i > x]

Answer 4

def threshold(a,x):
    vals = []
    for i in a:
        if i >= x: vals.append(i)
    return vals

Answer 5

I think the homework problem is to actually implement a filter function. Not just use the built in one.

def custom_filter(a,x):
    result = []
    for i in a:
        if i >= x:
            result.append(i)
    return result