解释Python中的数字范围

Question

在Pylons webapp中,我需要使用诸如"<3,45,46,48-51,77"之类的字符串,并创建要搜索的整数列表(实际上是对象的ID).

有关如何做到这一点的任何建议？我是Python的新手,我没有找到任何有助于这种事情的东西.

名单将是:[1,2,3,45,46,48,49,50,51,77]

Answer 1

从这里使用parseIntSet

我也喜欢最后评论中的pyparsing实现.

此处已修改parseIntSet以处理"<3"类型的条目,并且仅在无效字符串中吐出(如果有).

#! /usr/local/bin/python
import sys
import os

# return a set of selected values when a string in the form:
# 1-4,6
# would return:
# 1,2,3,4,6
# as expected...

def parseIntSet(nputstr=""):
    selection = set()
    invalid = set()
    # tokens are comma seperated values
    tokens = [x.strip() for x in nputstr.split(',')]
    for i in tokens:
        if len(i) > 0:
            if i[:1] == "<":
                i = "1-%s"%(i[1:])
        try:
            # typically tokens are plain old integers
            selection.add(int(i))
        except:
            # if not, then it might be a range
            try:
                token = [int(k.strip()) for k in i.split('-')]
                if len(token) > 1:
                    token.sort()
                    # we have items seperated by a dash
                    # try to build a valid range
                    first = token[0]
                    last = token[len(token)-1]
                    for x in range(first, last+1):
                        selection.add(x)
            except:
                # not an int and not a range...
                invalid.add(i)
    # Report invalid tokens before returning valid selection
    if len(invalid) > 0:
        print "Invalid set: " + str(invalid)
    return selection
# end parseIntSet

print 'Generate a list of selected items!'
nputstr = raw_input('Enter a list of items: ')

selection = parseIntSet(nputstr)
print 'Your selection is: '
print str(selection)

这是样本运行的输出:

$ python qq.py
Generate a list of selected items!
Enter a list of items: <3, 45, 46, 48-51, 77
Your selection is:
set([1, 2, 3, 45, 46, 77, 48, 49, 50, 51])