Python 在文件中的模式之后迭代 grep 行

Question

我有一个看起来像这样的文件:

~~~~~~~~~~~~~~~~~~~~~
Start
2, 0.001, 1.0
alpha = 0.001
beta = 1.3

...
...
...

new evaluation
complete
print out alpha & beta
alpha = 0.19
beta = 1.41
End

~~~~~~~~~~~~~~~~~~~~~
Start
....

我想提取“Start”后的三行和“print out”后的两行。基本上，它应该是:

~~~~~~~~~~~~~~~~~~~~~
2, 0.001, 1.0
alpha = 0.001
beta = 1.3

alpha = 0.19
beta = 1.41

~~~~~~~~~~~~~~~~~~~~~

这是我用的:

summary = open("summary_accuracy.txt","w")
content = []
with open(filename,'r') as f:
    for line in f:
        if "Start" in line:
            content += [f.readline() for i in range(3)]
        if "print out" in line:
            content += [f.readline() for i in range(2)]
            content += "~~~~~~~~~~"

summary.write(content)

但是，我得到了错误:

content += [f.readline() for i in range(3)]
ValueError: Mixing iteration and read methods would lose data

Answer 1

尝试使用 next(f) 而不是 f.readline()。

也可以考虑使用 regular expressions对于这个任务:

>>> import re
>>> re.search(r'^Start\s(.*\s.*\s.*\s)', s, re.MULTILINE).group(1)
'2, 0.001, 1.0\nalpha = 0.001\nbeta = 1.3\n'
>>> re.search(r'^print out.*\s(.*\s.*\s)', s, re.MULTILINE).group(1)
'alpha = 0.19\nbeta = 1.41\n'