取得Python代码段的正则表达式?

如：
def aa(i):
print i
a=[1,2,3]
b=2
c=3

能识别出起始位def aa(i):
和结束位" a=[1,2,3]"？

---

像Python对语法这么要求严格的我觉得就不要用正则了，效率不高。直接用判断就可以了，我写了个识别顶级函数的，抛砖引玉：
Python code:
s = r'''
def aa(i):
print i
a=[1,2,3]
b=2
c=3
def a():
print\
'w'
'''

def findFunc(s):
result = []
begin = False
def show(x): print '\n***Function***:\n', '\n'.join(x)

ss = s.split('\n')
for i,row in enumerate(ss):
if len(row)==0: continue
if begin:
if row.startswith(' '):
result.append(row)
elif ss[i-1].endswith('\\'):
result.append(row)
else:
show(result)
begin = False
result = []
if row.startswith('def '):
begin = True
result.append(row)
show(result)

findFunc(s)

---

我觉得应该用ast 才能把他正确解释出来

e.g.,

import ast

class V(ast.NodeVisitor):
def visit_FunctionDef(self, node):
print 'def %s' % (node.name)

s='''
def aa(i):
print i
a = [ 1, 2, 3]

b = 2
c = 3
'''

t = ast.parse(s)
V().visit(t)