如何使用环视功能捕获数字？

Question

例如，我试图在任何'9781612680880'之前捕获数字'1'：

尝试

\d+(?=.*(?=978)))

如何解决此问题？

Answer 1

我猜测此表达式可能返回所需的数字，

([0-9]+)(?=.+?978[0-9]+)

Demo

测试

# coding=utf8
# the above tag defines encoding for this document and is for Python 2.x compatibility

import re

regex = r"([0-9]+)(?=.+?978[0-9]+)"

test_str = "1 x 97819834719734 some other text after that 1 x 97819834719734 some other text after that 1 x 97819834719734 some other text after that 1 x 97819834719734 some other text after that "

matches = re.finditer(regex, test_str, re.MULTILINE)

for matchNum, match in enumerate(matches, start=1):

    print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group()))

    for groupNum in range(0, len(match.groups())):
        groupNum = groupNum + 1

        print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum)))

# Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution.