python的yield、标准输入输出的使用练习

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分类专栏： python 文章标签： python

于 2020-03-09 12:12:31 首次发布

本文链接：https://blog.youkuaiyun.com/weixin_44033089/article/details/104749389

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需求背景是将一个test.txt文档内容转化为html文件

需要用到sys.argv,yield,re.sub,标准输入输出用法

test.txt内容

Welcome to World Wide Spam, Inc.

These are the corporate web pages of *World Wide Spam*, Inc. We hope
you find your stay enjoyable, and that you will sample many of our
products.

A short history of the company
World Wide Spam was started in the summer of 2000. The business
concept was to ride the dot-com wave and to make money both through
bulk email and by selling canned meat online.
After receiving several complaints from customers who weren't
satisfied by their bulk email, World Wide Spam altered their profile,
and focused 100% on canned goods. Today, they rank as the world's
13,892nd online supplier of SPAM.
Destinations
From this page you may visit several of our interesting web pages:
- What is SPAM? (http://wwspam.fu/whatisspam)
- How do they make it? (http://wwspam.fu/howtomakeit)
- Why should I eat it? (http://wwspam.fu/whyeatit)
How to get in touch with us
You can get in touch with us in *many* ways: By phone (555-1234), by
email (wwspam@wwspam.fu) or by visiting our customer feedback page
(http://wwspam.fu/feedback).

用来读文件内容的生成器block.py。函数+yield=生成器，可用next（f）或 for x in f实现迭代

#block.py
def line(file):
    with open(file) as f:
        for line in f.readlines():
            yield line  #迭代返回读取到的每一行
        yield '\n'      #最后一次迭代返回一个空行

def block(file):
    block=[]                             #创建一个空列表用来装段落
    for l in line(file):               
        if l.strip():                
            block.append(l)              #如果读取到的这行不为空则增加到列表中
        elif block:
            yield ''.join(block).strip() #如果读取到的这行为空则将列表中的元素合并到一起形成一个段落，并迭代返回
            block=[]

用来生成文章段落的生成器txt2html.py。sys.argv[1]用来读取命令行的第一个参数，re.sub正则替换(.+?)表示非贪婪模式
```
#txt2html.py
import re,sys
from blocks import *

print('<html><head><title>...</title><body>')

title=True
for b in block(sys.argv[1]):
    b=re.sub(r'\*(.+?)\*',r'<em>\1<em>',b)
    if title:
        print('<h1>')
        print(b)
        print('<h1>')
        title=False
    else:
        print('<p>')
        print(b)
        print('<p>')
print('</body></html>')
```
```
import re
a=r"'test01','test02','test03'"
b=re.sub(r"'(.+?)'",r"+\1+",a)
c=re.sub(r"'(.+)'",r"+\1+",a)
print(b)
print(c)
```
b：+test01+,+test02+,+test03+
c：+test01','test02','test03+ 可以看到使用非贪婪模式的b是将每个单引号都替换成了+，而使用非贪婪模式的c之后最前和最后的单引号替换成了+。也就说明在贪婪模式下会从开始一直匹配到最后一个匹配的字符，中间即使有匹配上的也会忽略。而非贪婪模式下，会按最短距离匹配。
调用命令。标准输入（<）输出（>）
```
python txt2html.py e:\test.sql > e:\out.html
```