Mingjian's Blog

这三个概念是Python为了解决容器对象遍历问题抽象出来的概念. 三者之间的关系是:\(\text{generator}\subset\text{iterator}\subset\text{iterable}\).

这篇主要是翻译了一些官方文档The Python Language Reference第四章的干货, 加入一些自己理解的形象化描述以及一些例子代码. 写这篇的原因是工作原因做了一个从把VBScript转换成Python的工具, 需要复习一遍python的一些基础知识.

由于一个工作需要把大量的vbscript脚本转换成python脚本, 需要学习一下python的ast模块, 本文是一些干货的笔记. 由于当前最新的python 3.8的官方文档过于简略, 主要参考和翻译绿树蛇的文档和python3.10pre的文档.

AST是Abstract Syntax Trees的缩写, 中文是抽象语法树.

AST和code的转换

python代码有三个分身,

1. 以unicode字符串存在的源代码. 人类可读写, python解释器不可读.
2. 以AST对象存在的抽象语法树. 人类可读写, 但很难读懂原来的语义, 用来显示python语义元素之间的关系. 是从源代码翻译成目标代码的中间产品.
3. 以code object存在的可执行的目标代码. python解释器可读, 人类不可读.

\(\def\tauequ{\mathbin{\vDash\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\Dashv{\mathbin{\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\DEF{\sf{D\scriptsize EF}.\quad}\) \(\def\DEFi{\sf{D\scriptsize EF}^*.\quad}\) \(\def\DEFn{\sf{D\scriptsize EF}_*.\quad}\) \(\def\DEFin{\sf{D\scriptsize EF}^*_*.\quad}\) \(\def\llbracket{\unicode{x27E6}}\) \(\def\rrbracket{\unicode{x27E7}}\) \(\def\PROOF{\sf{P\scriptsize ROOF}.\quad}\)

点击这里进入AMIL目录

Problem 1

Show that (a) \(\Gamma;\alpha\vDash\varphi\) iff \(\Gamma\vDash(\alpha\rightarrow\varphi)\); and (b) \(\varphi\tauequ\psi\) iff \(\vDash(\varphi\leftrightarrow\psi)\).

\(\PROOF\)

\(\def\PROOF{\sf{P\scriptsize ROOF}.\quad}\)

点击这里进入AMIL目录

Problem 2

Show that no one of the following sentences is logically implied by the other two. (This is done by giving a structure in which the sentence in question is false, while the other two are true.)

1. \(\forall{x}\forall{y}\forall{z}(Pxy\rightarrow Pyz\rightarrow Pxz).\) Recall that by our convention \(\alpha\rightarrow\beta\rightarrow\gamma\) is \(\alpha\rightarrow(\beta\rightarrow\gamma).\)
2. \(\forall{x}\forall{y}(Pxy\rightarrow Pyx\rightarrow x=y).\)
3. \(\forall{x}\exists{y}Pxy\rightarrow\exists{y}\forall{x}Pxy.\)

听了得到上冯雪的科学减肥课. 把干货总结一下.

\(\def\tauequ{\mathbin{\vDash\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\Dashv{\mathbin{\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\DEF{\sf{D\scriptsize EF}.\quad}\) \(\def\DEFi{\sf{D\scriptsize EF}^*.\quad}\) \(\def\DEFn{\sf{D\scriptsize EF}_*.\quad}\) \(\def\DEFin{\sf{D\scriptsize EF}^*_*.\quad}\) \(\def\llbracket{\unicode{x27E6}}\) \(\def\rrbracket{\unicode{x27E7}}\) \(\def\PROOF{\sf{P\scriptsize ROOF}.\quad}\)

这是一个关于数理逻辑的读书笔记或者学习总结, 书名是A Mathematical Introduction to Logic, 作者Herbert B. Enderton, University of California

本文是Chapter 2, Section 2.2, 点击这里进入AMIL目录

\(\def\tauequ{\mathbin{\vDash\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\Dashv{\mathbin{\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\DEF{\sf{D\scriptsize EF}.\quad}\) \(\def\DEFi{\sf{D\scriptsize EF}^*.\quad}\) \(\def\DEFn{\sf{D\scriptsize EF}_*.\quad}\) \(\def\DEFin{\sf{D\scriptsize EF}^*_*.\quad}\) \(\def\llbracket{\unicode{x27E6}}\) \(\def\rrbracket{\unicode{x27E7}}\) \(\def\PROOF{\sf{P\scriptsize ROOF}.\quad}\)

这是一个关于数理逻辑的读书笔记或者学习总结, 书名是A Mathematical Introduction to Logic, 作者Herbert B. Enderton, University of California

本文是Chapter 2, Section 2.1 点击这里进入AMIL目录

\(\def\tauequ{\mathbin{\vDash\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\Dashv{\mathbin{\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\DEF{\sf{D\scriptsize EF}.\quad}\) \(\def\DEFi{\sf{D\scriptsize EF}^*.\quad}\) \(\def\DEFn{\sf{D\scriptsize EF}_*.\quad}\) \(\def\DEFin{\sf{D\scriptsize EF}^*_*.\quad}\)

这是一个关于数理逻辑的读书笔记或者学习总结, 书名是A Mathematical Introduction to Logic, 作者Herbert B. Enderton, University of California

本文是Chapter 1, Section 1.7, 点击这里进入AMIL目录

\(\def\tauequ{\mathbin{\vDash\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\Dashv{\mathbin{\style{display: inline-block; transform: scaleX(-1)}{\vDash}}}\) \(\def\DEF{\sf{D\scriptsize EF}.\quad}\) \(\def\DEFi{\sf{D\scriptsize EF}^*.\quad}\) \(\def\DEFn{\sf{D\scriptsize EF}_*.\quad}\) \(\def\DEFin{\sf{D\scriptsize EF}^*_*.\quad}\)

这是一个关于数理逻辑的读书笔记或者学习总结, 书名是A Mathematical Introduction to Logic, 作者Herbert B. Enderton, University of California

本文是Chapter 1, Section 1.1, 1.2, 点击这里进入AMIL目录