英文:
Python reading text file every second line skipped
问题
f = open("sample_failing_file.txt", encoding="ISO-8859-1")
readfile = f.read()
filelines = readfile.split("\n")
def remove_irrelevant_lines(filecontent: list[str]) -> list[str]:
filecontent_copy = filecontent.copy()
for line in filecontent_copy:
if drop_line_appropriate(line):
filecontent.remove(line)
return filecontent
def drop_line_appropriate(line: str) -> bool:
if line.startswith("#"):
return True
# some more conditions, omitted here
return False
filelines = remove_irrelevant_lines(filelines)
f.close()
英文:
I am processing a shell script in Python. My first step is to comb through the file and save only the important lines in a list (of strings). However, I have isolated a problem where every second line is ignored. Why is the second, fourth, etc. line skipped in the following code?
f = open("sample_failing_file.txt", encoding="ISO-8859-1")
readfile = f.read()
filelines = readfile.split("\n")
def remove_irrelevant_lines(filecontent: list[str]) -> list[str]:
for line in filecontent:
if drop_line_appropriate(line):
filecontent.remove(line)
return filecontent
def drop_line_appropriate(line: str) -> bool:
if line.startswith("#"):
return True
# some more conditions, omitted here
return False
filelines = remove_irrelevant_lines(filelines)
f.close()
When I run this code, I can see filecontent is complete. However, when I look at line, I can see e.g. some line 3 is never read. Here is a simplified version of the shell script, on which my Python script fails (sample_failing_file.txt)
#!/bin/sh
#
# some line 1
#
# some line 2
# some line 3
答案1
得分: 0
正如评论中指出的，不应在迭代列表时尝试删除元素。此外，在删除行时，不要使用 list.remove()，因为这会导致它搜索该行，使其运行速度远远慢于应有的速度。
以下代码应该解决您的问题，并且运行速度会更快：
def remove_irrelevant_lines(filecontent: list[str]) -> list[str]:
return
这将创建并返回一个新列表，过滤掉由 drop_line_appropriate 指示的行。
英文:
As was pointed out in the comments, you shouldn't try to remove elements from a list while iterating over it. Additionally, when removing lines, don't want to use list.remove(), since that causes it to search for the line, which will make it run vastly slower than it should.
The following should fix your problem and also run vastly faster:
def remove_irrelevant_lines(filecontent: list[str]) -> list[str]:
return
This creates and returns a new list, filtering out the lines indicated by drop_line_appropriate.
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