类似AWK的文本处理

import re

class AwkUnhandledLine( RuntimeError ):
pass

class Awk:
"""awk-like mapping from patterns to handlers."""
def __init__(self):
# Start without any patterns
self.pats=[]
def add(self,pattern,handler=None):
# Add a pattern and its handler,
# precompiling the pattern
self.pats.append((re.compile(pattern),handler))
def process(self,line):
# Find the first pattern that matches the input,
# and call the handler with the result of the match.
for pat, handler in self.pats:
m = pat.match(line)
if m:
if callable(handler):
return handler(**m.groupdict())
else:
return handler
raise AwkUnhandledLine( line )

class AwkFileInput(Awk):
def __init__(self):
import fileinput
self.fileinput = fileinput
Awk.__init__(self)
def processinput(self):
for line in self.fileinput.input():
try:
self.process(line)
except AwkUnhandledLine, e:
raise AwkUnhandledLine(
"Don't understand line %d of file %s: %s" %
(fileinput.filelineno(),
fileinput.filename(),
line) )

# example:

def handle_thing(name=None,num=0):
if name:
print name, "=", float(num)
else:
print float(num), "has no name"

def example():
a = AwkFileInput()
a.add("^#") # Ignore comments (handler==None)
a.add("^(?P<num>\d+\.\d+)", handle_thing) # Print numbers
a.add("^(?P<name>\w+)\s+(?P<num>\d+)", handle_thing) # Print named numbers
a.processinput()