Question

所以我正在使用写这个方法，它在查找数字方面工作正常，但它只返回最后一个值。是否有一种方法可以使它在每次运行后返回所有值。这是我的代码：

def searchPFAM():

    fileAddress = '/Volumes/interpro/data/Q14591.txt'
    start = None
    end = None
    with open(fileAddress,'rb') as f:
        root = etree.parse(f)
        for lcn in root.xpath("/protein/match[@dbname='PFAM']/lcn"):#find dbname =PFAM
            start = int(lcn.get("start"))#if it is PFAM then look for start value
            end = int(lcn.get("end"))#if it is PFAM then also look for end value
            print start, end
        return start, end

Answer 1

你的意思是什么？

def do_something(fname):
    with open(fname,'rb') as f:
        root = etree.parse(f)
        for lcn in root.xpath("/protein/match[@dbname='PFAM']/lcn"):#find dbname =PFAM
            # Make slightly more robust
            try:
                start = int(lcn.get("start"))#if it is PFAM then look for start value
                end = int(lcn.get("end"))#if it is PFAM then also look for end value
                yield start, end
            except (TypeError , ValueError) as e:
                pass # start/end aren't usable as numbers decide what to do here...

for start, end in do_something():
    do_something_else(start, end)

Answer 2

您可以创建一个开始和结束元组的列表，只需在函数末尾返回列表。

Answer 3

只需修改您的函数即可创建并返回开始，结束元组的列表：

def searchPFAM():
    fileAddress = '/Volumes/interpro/data/Q14591.txt'
    start = None
    end = None
    result = []
    with open(fileAddress,'rb') as f:
        root = etree.parse(f)
        for lcn in root.xpath("/protein/match[@dbname='PFAM']/lcn"):#find dbname =PFAM
            start = int(lcn.get("start"))#if it is PFAM then look for start value
            end = int(lcn.get("end"))#if it is PFAM then also look for end value
            print start, end
        result.append((start, end))
    return result

稍微不那么可读，但更紧凑和有效的写作方式将是使用知识作为“列表理解”将是这样的：

def searchPFAM():
    fileAddress = '/Volumes/interpro/data/Q14591.txt'
    start = None
    end = None
    with open(fileAddress,'rb') as f:
        root = etree.parse(f)
        result = [(int(lcn.get("start")), int(lcn.get("end"))) 
                     for lcn in root.xpath("/protein/match[@dbname='PFAM']/lcn")]
    return result

之后您可以像这样处理返回的列表：

for start,end in result:
   ... # do something with pair of int values

或

for i in xrange(len(result)):
   start,end = result[i][0],result[i][1]
   ... # do something with pair of int values

如何使函数返回每个可能的值

3 个答案: