[英]how to skip blocks of text when writing file in python
Is it possible to use python to skip blocks of text when writing a file from another file?从另一个文件写入文件时,是否可以使用 python 跳过文本块?
For example lets say the input file is:例如,假设输入文件是:
This is the file I would like to write this line
I would like to skip this line
and this one...
and this one...
and this one...
but I want to write this one
and this one...
How can I write a script that allows me to skip certain lines that differ in content and size which resumes writing the lines to another file once it recognizes a certain line?我如何编写一个脚本,允许我跳过某些内容和大小不同的行,一旦它识别出某个行,它就会继续将这些行写入另一个文件?
My code reads through the lines, doesn't write duplicate lines and performs some operation on the line by using dictionaries and regex.我的代码通读行,不写重复行,并使用字典和正则表达式在行上执行一些操作。
def is_wanted(line):
#
# You have to define this!
#
# return True to keep the line, or False to discard it
def copy_some_lines(infname, outfname, wanted_fn=is_wanted):
with open(infname) as inf, open(outfname, "w") as outf:
outf.writelines(line for line in inf if wanted_fn(line))
copy_some_lines("file_a.txt", "some_of_a.txt")
In order to extend this to multi-line blocks, you can implement a finite state machine like为了将其扩展到多行块,您可以实现一个有限状态机,如
which would turn into something like这会变成类似的东西
class BlockState:
GOOD_BLOCK = True
BAD_BLOCK = False
def __init__(self):
self.state = self.GOOD_BLOCK
def is_bad(self, line):
# *** Implement this! ***
# return True if line is bad
def is_good(self, line):
# *** Implement this! ***
# return True if line is good
def __call__(self, line):
if self.state == self.GOOD_BLOCK:
if self.is_bad(line):
self.state = self.BAD_BLOCK
else:
if self.is_good(line):
self.state = self.GOOD_BLOCK
return self.state
then然后
copy_some_lines("file_a.txt", "some_of_a.txt", BlockState())
Pseudo-code:伪代码:
# Open input and output files, and declare the unwanted function
for line in file1:
if unwanted(line):
continue
file2.write(line)
# Close files etc...
You can read the file line by line, and have control on each line you read:您可以逐行读取文件,并控制您读取的每一行:
with open(<your_file>, 'r') as lines:
for line in lines:
# skip this line
# but not this one
Note that if you want to read all lines despite the content and only then manipulate it, you can:请注意,如果您想阅读所有行而不考虑内容,然后才对其进行操作,您可以:
with open(<your_file>) as fil:
lines = fil.readlines()
This should work:这应该有效:
SIZE_TO_SKIP = ?
CONTENT_TO_SKIP = "skip it"
with open("my/input/file") as input_file:
with open("my/output/file",'w') as output_file:
for line in input_file:
if len(line)!=SIZE_TO_SKIP and line!=CONTENT_TO_SKIP:
output_file.write(line)
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