如何查看Python函數的源代碼

05-25

如何查看Python函數的源代碼

來自專欄恆仔のPython

這兩天在寫code的時候，某個函數error，就想知道這個函數到底做了啥會報錯。

那當想知道一些函數的源代碼寫了什麼方法，想知道源代碼放在哪個路徑中，或者想將源代碼進行字元操作。該咋做呢？

這時候，我們可以用很簡單的方法來做Python函數源代碼的查看，Python中有兩個Libraries能夠使用：

inspect 一個Python內置的標準庫
drill 是一個第三方庫

inspect

inspect模塊用於收集python對象的信息，可以獲取類或函數的參數的信息，源碼，解析堆棧，對對象進行類型檢查等等

舉個栗子，用BeautifulSoup做分析，現在我們導入了兩個庫

import inspectfrom bs4 import BeautifulSoup

先看看BeautifulSoup的文檔定義

inspect.getdoc(BeautifulSoup)

輸出是：

This class defines the basic interface called by the tree builders.


These methods will be called by the parser:

  reset()

  feed(markup)
The tree builder may call these methods from its feed() implementation:

  handle_starttag(name, attrs) # See note about return value

  handle_endtag(name)

  handle_data(data) # Appends to the current data node

  endData(containerClass=NavigableString) # Ends the current data node
No matter how complicated the underlying parser is, you should be

able to build a tree using start tag events, end tag events,

data events, and "done with data" events.

If you encounter an empty-element tag (aka a self-closing tag, like HTMLs <br> tag), call handle_starttag and then handle_endtag.

再來看看BeautifulSoup存放的路徑

inspect.getsourcefile(BeautifulSoup)

輸出是

/Users/vincentyau/anaconda3/lib/python3.6/site-packages/bs4/__init__.py

重點來了，當想看源代碼的時候，可以用

inspect.getsourcelines(BeautifulSoup)

輸出是

([class BeautifulSoup(Tag): , """ , This class defines the basic interface called by the tree builders. , , These methods will be called by the parser: , reset() , feed(markup) , , The tree builder may call these methods from its feed() implementation: , handle_starttag(name, attrs) # See note about return value , handle_endtag(name) , handle_data(data) # Appends to the current data node , endData(containerClass=NavigableString) # Ends the current data node , , No matter how complicated the underlying parser is, you should be , " able to build a tree using start tag events, end tag events, ", data events, and "done with data" events. , ,注釋：太長了，我就截了一小段

如果你是用Python或者Notebook的話，inspect也可以查看你自己寫的函數，用法和上面的一樣。

但如果你是用terminal之類的Python編譯，來查看自己定義的函數，則會引發IOError: could not get source code。

dill

剛剛發現在百度搜索dill，還搜索不出相關的結果，說明dill還是很小眾，那官網的相關定義是

dill extends Pythons pickle module for serializing and deserializing Python objects to the majority of the built-in Python types. At the same time, it can also retrieve the source code of your Python objects. Please note dill is not a standard library, so you must install it separately.

翻譯一下

dill擴展了Python的pickle模塊，用於序列化和反序列化Python對象到大多數內置Python類型。同時，它還可以檢索Python對象的源代碼。請注意dill不是標準庫，所以必須單獨安裝它。

不過我還發現，Anaconda已經默認安裝了dill(⊙v⊙)嗯

那基本的用法是

import dill

獲得源代碼文件路徑

dill.source.getsourcefile(BeautifulSoup)

獲得源代碼

dill.source.getsourcelines(BeautifulSoup)

以上的輸出和inspect一樣，還有findsouce()函數

dill.source.findsource(BeautifulSoup)

這個的輸出是

(["""Beautiful Soup , Elixir and Tonic , "The Screen-Scrapers Friend" , http://www.crummy.com/software/BeautifulSoup/ , , Beautiful Soup uses a pluggable XML or HTML parser to parse a , (possibly invalid) document into a tree representation. Beautiful Soup , provides methods and Pythonic idioms that make it easy to navigate, , search, and modify the parse tree. , , Beautiful Soup works with Python 2.7 and up. It works better if lxml , and/or html5lib is installed. , , For more than you ever wanted to know about Beautiful Soup, see the , documentation: , http://www.crummy.com/software/BeautifulSoup/bs4/doc/ , , """ , , # Use of this source code is governed by a BSD-style license that can be , # found in the LICENSE file. ,注釋：太長了截一段

dill還有蠻多函數的，那dill和inspect有一個大的差別就是，你用Plain Python也能用dill查看自定義的函數，而inspect則會報錯

參考資料：

[1] How to retrieve source code of Python functions

[2] Inspect Document

[3] DILL