方法1，python内置help()
In [1]: help(len)
Help on built-in function len in module builtins:
len(...)
len(object) -> integer
Return the number of items of a sequence or mapping.
方法2，简化的问号？
In [2]: len?
Type: builtin_function_or_method
String form: <built-in function len>
Namespace: Python builtin
Docstring:
len(object) -> integer
Return the number of items of a sequence or mapping.
也可以对object的方法或object本身使用问号
object的方法：
In [3]: L = [1, 2, 3]
In [4]: L.insert?
Type: builtin_function_or_method
String form: <built-in method insert of list object at 0x1024b8ea8>
Docstring: L.insert(index, object) -- insert object before index
object本身：
In [5]: L?
Type: list
String form: [1, 2, 3]
Length: 3
Docstring:
list() -> new empty list
list(iterable) -> new list initialized from iterable's items
也就是说，可以对function使用问号：
In [6]: def square(a):
....: """Return the square of a."""
....: return a ** 2
....:
In [7]: square?
Type: function
String form: <function square at 0x103713cb0>
Definition: square(a)
Docstring: Return the square of a.
连用2个问号？？可以拿到function的源代码：
In [8]: square??
Type: function
String form: <function square at 0x103713cb0>
Definition: square(a)
Source:
def square(a):
"Return the square of a"
return a ** 2
但是python内置函数后面跟??很可能只得到跟?一样的结果：
In [9]: len??
Type: builtin_function_or_method
String form: <built-in function len>
Namespace: Python builtin
Docstring:
len(object) -> integer
Return the number of items of a sequence or mapping.
在对象后面加.<TAB>可以获得这个对象的属性：
In [10]: L.<TAB>
L.append L.copy L.extend L.insert L.remove L.sort
L.clear L.count L.index L.pop L.reverse
可以再加字符缩小范围：
In [10]: L.c<TAB>
L.clear L.copy L.count
In [10]: L.co<TAB>
L.copy L.count
在对象后面加._<TAB>可以看到对象的隐藏属性：
In [10]: L._<TAB>
L.__add__ L.__gt__ L.__reduce__
L.__class__ L.__hash__ L.__reduce_ex__
Tab填补：知道起始字符的时候也可以用来填补输入
In [10]: from itertools import co<TAB>
combinations compress
combinations_with_replacement count
In [10]: import h<TAB>
hashlib hmac http
heapq html husl
*：Tab只能知道起始字符的时候朝后填补，当你不知道起始字符的时候可以用星号
In [10]: *Warning?
BytesWarning RuntimeWarning
DeprecationWarning SyntaxWarning
FutureWarning UnicodeWarning
ImportWarning UserWarning
PendingDeprecationWarning Warning
ResourceWarning
星号代表任何字符，包括空字符，
所以如果你想找包含find的string相关的method，可以这样找：
In [10]: str.*find*?
str.find
str.rfind
