根据正则表达式选择调用的Python函数

Question

有没有办法把一个函数放进数据结构里，而不先用def给它起个名字呢？

# This is the behaviour I want. Prints "hi".
def myprint(msg):
    print msg
f_list = [ myprint ]
f_list[0]('hi')
# The word "myprint" is never used again. Why litter the namespace with it?

不过，lambda函数的功能很有限，所以我不能用它们。

补充说明：为了更好地说明问题，这里有一段我在实际编码中遇到的代码。

def handle_message( msg ):
    print msg
def handle_warning( msg ):
    global num_warnings, num_fatals
    num_warnings += 1
    if ( is_fatal( msg ) ):
        num_fatals += 1
handlers = (
    ( re.compile( '^<\w+> (.*)' ), handle_message ),
    ( re.compile( '^\*{3} (.*)' ), handle_warning ),
)
# There are really 10 or so handlers, of similar length.
# The regexps are uncomfortably separated from the handler bodies,
# and the code is unnecessarily long.

for line in open( "log" ):
    for ( regex, handler ) in handlers:
        m = regex.search( line )
        if ( m ): handler( m.group(1) )

Answer 1

继续Gareth的简洁方法，这里提供一个模块化且自包含的解决方案：

import re

# in util.py
class GenericLogProcessor(object):

    def __init__(self):
      self.handlers = [] # List of pairs (regexp, handler)

    def register(self, regexp):
        """Declare a function as handler for a regular expression."""
        def gethandler(f):
            self.handlers.append((re.compile(regexp), f))
            return f
        return gethandler

    def process(self, file):
        """Process a file line by line and execute all handlers by registered regular expressions"""
        for line in file:
            for regex, handler in self.handlers:
                m = regex.search(line)
                if (m):
                  handler(m.group(1))      

# in log_processor.py
log_processor = GenericLogProcessor()

@log_processor.register(r'^<\w+> (.*)')
def handle_message(msg):
    print msg

@log_processor.register(r'^\*{3} (.*)')
def handle_warning(msg):
    global num_warnings, num_fatals
    num_warnings += 1
    if is_fatal(msg):
        num_fatals += 1

# in your code
with open("1.log") as f:
  log_processor.process(f)

Answer 2

更好更简洁的方式来解决你实际的问题：

def message(msg):
    print msg
message.re = '^<\w+> (.*)'

def warning(msg):
    global num_warnings, num_fatals
    num_warnings += 1
    if ( is_fatal( msg ) ):
        num_fatals += 1
warning.re = '^\*{3} (.*)'

handlers = [(re.compile(x.re), x) for x in [
        message,
        warning,
        foo,
        bar,
        baz,
    ]]

Answer 3

这段内容是基于Udi的一个很好的回答。

我觉得创建匿名函数的难度其实有点误导。你真正想做的是把相关的代码放在一起，让代码看起来整洁。所以我认为装饰器可能会对你有帮助。

import re

# List of pairs (regexp, handler)
handlers = []

def handler_for(regexp):
    """Declare a function as handler for a regular expression."""
    def gethandler(f):
        handlers.append((re.compile(regexp), f))
        return f
    return gethandler

@handler_for(r'^<\w+> (.*)')
def handle_message(msg):
    print msg

@handler_for(r'^\*{3} (.*)')
def handle_warning(msg):
    global num_warnings, num_fatals
    num_warnings += 1
    if is_fatal(msg):
        num_fatals += 1