Python 3.x：如何换行

Question

我有一个小脚本，可以从.html文件中提取一些文本。

f = open(local_file,"r")
for line in f:
    searchphrase = '<span class="position'
    if searchphrase in line:
        print("found it\n")

这对我来说没问题（错误处理稍后会导入），我的问题是我想要提取的文本跟搜索短语相隔两行。怎样才能在 .html 文件中向下移动两行？

- SaintCore

Answer 1

您可以通过连续两次调用 next() 方法，将可迭代对象 f 推进两行：

with open(local_file,"r") as f
    for line in f:
        searchphrase = '<span class="position'
        if searchphrase in line:
            print("found it\n")
            next(f) # skip 1 line
            return next(f)  # and return the line after that.

然而，如果你想解析HTML，请考虑使用HTML解析器代替。例如使用BeautifulSoup。

- Martijn Pieters

Answer 2

这对我很有效：

f = open(local_file,"r")
found = -1
for line in f:
    if found == 2:
        print("Line: "+line);
        break
    elif found > 0:
        found += 1
    else:
        searchphrase = '<span class="position'
        if searchphrase in line:
            print("found it")
            found = 1

输入文件为：

bla
<span class="position">Hello</span>
blub
that's it
whatever

程序的输出结果：

found it
Line: that's it

你可以将break替换为将found重置为-1，以搜索模式的更多出现...

- Michael