CS251 - Python

Introduction

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Python is an interpreted language; meanwhile C++ is a compiled Language.

Compiling: Check Syntax -> Semantic Analysis -> Optimizations -> Convert optimized to x86-64 program. This x86-64 program can be run as many times as needed. Semantic Analysis is Static in nature.

Interpretation: Syntax Analysis -> ByteCode Generator -> ByteCode Optimization. This ByteCode runs on a Virtual Machine Simulator which runs (gets Interpreted) on your laptop. The Semantic Analysis in this case is dynamic, meaning that it occurs when the ByteCode is being executed.

ByteCode Analysis

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import dis is the module to be imported; and to view the ByteCode of a function, do dis.dis(<function_name>).

The output of the corresponding code should be in the format of 5 columns.

Python Line	>>	Functions being done	???	Variable name
Points to the line in the original Python File to which the stack corresponds to	Present means that a pointer (of sorts) is stored to the particular line. Done when a “jump” to the line is needed to be done; usually for for, while or else cases.	All the stuff that the Virtual Machine does at the corresponding line, in sequence.	Address of the variable or smth?	The corresponding variable name in the Python File, or the value of the corresponding constant in the Python File.

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To run a python script from the Python Shell; do exec(open('<YourFile>.py').read()). After the script has been executed; you can print any variables in the environment without adding print() statements and running it again.

This might help in debugging the code faster.

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Operator Hacks

• x = n // 2 does integer division of n and 2. That means this is similar to int(n/2).

Usage of Basic Functions

• print(var, end = '<ending char>') – Print n and the character in end after it. By default; end = \n.
• input(<string>) – Prints <string> and waits for input in the same line.