Binary Buffers and I/O Errors

Introduction

This is the second lesson of chapter 13 in the Comprehensions, Lambdas, Closures, and I/O section of PCAP-31-03 (22% of the score, 9 of 40 items). It covers objectives 5.4 and 5.5 for binary data, and objective 2.1 for the errors that file operations raise. In the previous lesson you worked with text streams. Here you handle raw bytes: the bytearray type, binary files opened with "rb" and "wb", buffers filled by readinto(), and the OSError family with its errno attribute.