I have an app that parses multiple Cisco show tech files. These files contain the output of multiple router commands in a structured way, let me show you an snippet of a show tech output:
`show clock`
20:20:50.771 UTC Wed Sep 07 2022
Time source is NTP
`show callhome`
callhome disabled
Callhome Information:
<SNIPET>
`show module`
Mod Ports Module-Type Model Status
--- ----- ------------------------------------- --------------------- ---------
1 52 16x10G + 32x10/25G + 4x100G Module N9K-X96136YC-R ok
2 52 16x10G + 32x10/25G + 4x100G Module N9K-X96136YC-R ok
3 52 16x10G + 32x10/25G + 4x100G Module N9K-X96136YC-R ok
4 52 16x10G + 32x10/25G + 4x100G Module N9K-X96136YC-R ok
21 0 Fabric Module N9K-C9504-FM-R ok
22 0 Fabric Module N9K-C9504-FM-R ok
23 0 Fabric Module N9K-C9504-FM-R ok
<SNIPET>
My app currently uses both SED and Python scripts to parse these files. I use SED to parse the show tech file looking for a specific command output, once I find it, I stop SED. This way I don't need to read all the file (these can get to be very big files). This is a snipet of my SED script:
sed -E -n '/`show running-config`|`show running`|`show running config`/{
p
:loop
n
p
/`show/q
b loop
}' $1/$file
As you can see I am using a multi address range in SED. My question specifically is, how can I achieve something similar in python? I have tried multiple combinations of flags: DOTALL and MULTILINE but I can't get the result I'm expecting, for example, I can get a match for the command I'm looking for, but python regex wont stop until the end of the file after the first match.
I am looking for something like this
sed -n '/`show clock`/,/`show/p'
I would like the regex match to stop parsing the file and print the results, immediately after seeing `show again , hope that makes sense and thank you all for reading me and for your help
You can use nested loops.
import re
def process_file(filename):
with open(filename) as f:
for line in f:
if re.search(r'`show running-config`|`show running`|`show running config`', line):
print(line)
for line1 in f:
print(line1)
if re.search(r'`show', line1):
return
The inner for loop will start from the next line after the one processed by the outer loop.
You can also do it with a single loop using a flag variable.
import re
def process_file(filename):
in_show = False
with open(filename) as f:
for line in f:
if re.search(r'`show running-config`|`show running`|`show running config`', line):
in_show = True
if in_show
print(line)
if re.search(r'`show', line1):
return
After looking all over the Internet, I've come to this.
Let's say I have already made a text file that reads:
Hello World
Well, I want to remove the very last character (in this case d) from this text file.
So now the text file should look like this: Hello Worl
But I have no idea how to do this.
All I want, more or less, is a single backspace function for text files on my HDD.
This needs to work on Linux as that's what I'm using.
Use fileobject.seek() to seek 1 position from the end, then use file.truncate() to remove the remainder of the file:
import os
with open(filename, 'rb+') as filehandle:
filehandle.seek(-1, os.SEEK_END)
filehandle.truncate()
This works fine for single-byte encodings. If you have a multi-byte encoding (such as UTF-16 or UTF-32) you need to seek back enough bytes from the end to account for a single codepoint.
For variable-byte encodings, it depends on the codec if you can use this technique at all. For UTF-8, you need to find the first byte (from the end) where bytevalue & 0xC0 != 0x80 is true, and truncate from that point on. That ensures you don't truncate in the middle of a multi-byte UTF-8 codepoint:
with open(filename, 'rb+') as filehandle:
# move to end, then scan forward until a non-continuation byte is found
filehandle.seek(-1, os.SEEK_END)
while filehandle.read(1) & 0xC0 == 0x80:
# we just read 1 byte, which moved the file position forward,
# skip back 2 bytes to move to the byte before the current.
filehandle.seek(-2, os.SEEK_CUR)
# last read byte is our truncation point, move back to it.
filehandle.seek(-1, os.SEEK_CUR)
filehandle.truncate()
Note that UTF-8 is a superset of ASCII, so the above works for ASCII-encoded files too.
Accepted answer of Martijn is simple and kind of works, but does not account for text files with:
UTF-8 encoding containing non-English characters (which is the default encoding for text files in Python 3)
one newline character at the end of the file (which is the default in Linux editors like vim or gedit)
If the text file contains non-English characters, neither of the answers provided so far would work.
What follows is an example, that solves both problems, which also allows removing more than one character from the end of the file:
import os
def truncate_utf8_chars(filename, count, ignore_newlines=True):
"""
Truncates last `count` characters of a text file encoded in UTF-8.
:param filename: The path to the text file to read
:param count: Number of UTF-8 characters to remove from the end of the file
:param ignore_newlines: Set to true, if the newline character at the end of the file should be ignored
"""
with open(filename, 'rb+') as f:
last_char = None
size = os.fstat(f.fileno()).st_size
offset = 1
chars = 0
while offset <= size:
f.seek(-offset, os.SEEK_END)
b = ord(f.read(1))
if ignore_newlines:
if b == 0x0D or b == 0x0A:
offset += 1
continue
if b & 0b10000000 == 0 or b & 0b11000000 == 0b11000000:
# This is the first byte of a UTF8 character
chars += 1
if chars == count:
# When `count` number of characters have been found, move current position back
# with one byte (to include the byte just checked) and truncate the file
f.seek(-1, os.SEEK_CUR)
f.truncate()
return
offset += 1
How it works:
Reads only the last few bytes of a UTF-8 encoded text file in binary mode
Iterates the bytes backwards, looking for the start of a UTF-8 character
Once a character (different from a newline) is found, return that as the last character in the text file
Sample text file - bg.txt:
Здравей свят
How to use:
filename = 'bg.txt'
print('Before truncate:', open(filename).read())
truncate_utf8_chars(filename, 1)
print('After truncate:', open(filename).read())
Outputs:
Before truncate: Здравей свят
After truncate: Здравей свя
This works with both UTF-8 and ASCII encoded files.
In case you are not reading the file in binary mode, where you have only 'w' permissions, I can suggest the following.
f.seek(f.tell() - 1, os.SEEK_SET)
f.write('')
In this code above, f.seek() will only accept f.tell() b/c you do not have 'b' access. then you can set the cursor to the starting of the last element. Then you can delete the last element by an empty string.
with open(urfile, 'rb+') as f:
f.seek(0,2) # end of file
size=f.tell() # the size...
f.truncate(size-1) # truncate at that size - how ever many characters
Be sure to use binary mode on windows since Unix file line ending many return an illegal or incorrect character count.
with open('file.txt', 'w') as f:
f.seek(0, 2) # seek to end of file; f.seek(0, os.SEEK_END) is legal
f.seek(f.tell() - 2, 0) # seek to the second last char of file; f.seek(f.tell()-2, os.SEEK_SET) is legal
f.truncate()
subject to what last character of the file is, could be newline (\n) or anything else.
This may not be optimal, but if the above approaches don't work out, you could do:
with open('myfile.txt', 'r') as file:
data = file.read()[:-1]
with open('myfile.txt', 'w') as file:
file.write(data)
The code first opens the file, and then copies its content (with the exception of the last character) to the string data. Afterwards, the file is truncated to zero length (i.e. emptied), and the content of data is saved to the file, with the same name.
This is basically the same as vins ms's answer, except that it doesn't use the os package, and that is used the safer 'with open' syntax. This may not be recommended if the text file is huge. (I wrote this since none of the above approaches worked out too well for me in python 3.8).
here is a dirty way (erase & recreate)...
i don't advice to use this, but, it's possible to do like this ..
x = open("file").read()
os.remove("file")
open("file").write(x[:-1])
On a Linux system or (Cygwin under Windows). You can use the standard truncate command. You can reduce or increase the size of your file with this command.
In order to reduce a file by 1G the command would be truncate -s 1G filename. In the following example I reduce a file called update.iso by 1G.
Note that this operation took less than five seconds.
chris#SR-ENG-P18 /cygdrive/c/Projects
$ stat update.iso
File: update.iso
Size: 30802968576 Blocks: 30081024 IO Block: 65536 regular file
Device: ee6ddbceh/4000177102d Inode: 19421773395035112 Links: 1
Access: (0664/-rw-rw-r--) Uid: (1052727/ chris) Gid: (1049089/Domain Users)
Access: 2020-06-12 07:39:00.572940600 -0400
Modify: 2020-06-12 07:39:00.572940600 -0400
Change: 2020-06-12 07:39:00.572940600 -0400
Birth: 2020-06-11 13:31:21.170568000 -0400
chris#SR-ENG-P18 /cygdrive/c/Projects
$ truncate -s -1G update.iso
chris#SR-ENG-P18 /cygdrive/c/Projects
$ stat update.iso
File: update.iso
Size: 29729226752 Blocks: 29032448 IO Block: 65536 regular file
Device: ee6ddbceh/4000177102d Inode: 19421773395035112 Links: 1
Access: (0664/-rw-rw-r--) Uid: (1052727/ chris) Gid: (1049089/Domain Users)
Access: 2020-06-12 07:42:38.335782800 -0400
Modify: 2020-06-12 07:42:38.335782800 -0400
Change: 2020-06-12 07:42:38.335782800 -0400
Birth: 2020-06-11 13:31:21.170568000 -0400
The stat command tells you lots of info about a file including its size.
I am trying to write Chinese characters to a CSV file based on their Unicode code points found in a text file in unicode.org/Public/zipped/13.0.0/Unihan.zip. For instance, one example character is U+9109.
In the example below I can get the correct output by hard coding the value (line 8), but keep getting it wrong with every permutation I've tried at generating the bytes from the code point (lines 14-16).
I'm running this in Python 3.8.3 on a Debian-based Linux distro.
Minimal working (broken) example:
1 #!/usr/bin/env python3
2
3 def main():
4
5 output = open("test.csv", "wb")
6
7 # Hardcoded values work just fine
8 output.write('\u9109'.encode("utf-8"))
9
10 # Comma separation
11 output.write(','.encode("utf-8"))
12
13 # Problem is here
14 codepoint = '9109'
15 u_str = '\\' + 'u' + codepoint
16 output.write(u_str.encode("utf-8"))
17
18 # End with newline
19 output.write('\n'.encode("utf-8"))
20
21 output.close()
22
23 if __name__ == "__main__":
24 main()
Executing and viewing results:
example $
example $./test.py
example $
example $cat test.csv
鄉,\u9109
example $
The expected output would look like this (Chinese character occurring on both sides of the comma):
example $
example $./test.py
example $cat test.csv
鄉,鄉
example $
chr is used to convert integers to code points in Python 3. Your code could use:
output.write(chr(0x9109).encode("utf-8"))
But if you specify the encoding in the open instead of using binary mode you don't have to manually encode everything. print to a file handles newlines for you as well.
with open("test.txt",'w',encoding='utf-8') as output:
for i in range(0x4e00,0x4e10):
print(f'U+{i:04X} {chr(i)}',file=output)
Output:
U+4E00 一
U+4E01 丁
U+4E02 丂
U+4E03 七
U+4E04 丄
U+4E05 丅
U+4E06 丆
U+4E07 万
U+4E08 丈
U+4E09 三
U+4E0A 上
U+4E0B 下
U+4E0C 丌
U+4E0D 不
U+4E0E 与
U+4E0F 丏
This question already has an answer here:
How to catch all exceptions in Try/Catch Block Python?
(1 answer)
Closed 3 years ago.
My code below goes through each .m4v file in the list and converts them to a .wav file using FFmpeg, and it works. I use python 3 jupyter environment.
for fpath in list:
if (fpath.endswith(".m4v")):
cdir=os.path.dirname(fpath)
os.chdir(cdir)
filename=os.path.basename(fpath)
os.system("ffmpeg -i {0} temp_name.wav".format(filename))
ofnamepath=os.path.splitext(fpath)[0]
temp_name=os.path.join(cdir, "temp_name.wav")
new_name = os.path.join(ofnamepath+'.wav')
os.rename(temp_name,new_name)
old_name=os.path.join(ofnamepath+'.m4v')
os.remove(old_name)
However, for this particular dataset I get the following error;
> UnicodeEncodeError Traceback (most recent call
> last) <ipython-input-10-bd3b17e409fa> in <module>()
>
>
> > 7 os.chdir(cdir)
> > 8 filename=os.path.basename(fpath)
> > ----> 9 os.system("ffmpeg -i {0} temp_name.wav".format(filename))
> > 10 ofnamepath=os.path.splitext(fpath)[0]
> > 11 temp_name=os.path.join(cdir, "temp_name.wav")
>
> UnicodeEncodeError: 'ascii' codec can't encode characters in position
> 10-16: ordinal not in range(128)
Is it possible to do add an if comment line in the code something like;
if 'UnicodeEncodeError: 'ascii' codec can't encode'
delete that file and continue to the next file?
You can use a try and except block.
If an exception occurs while inside a try block, it will jump to the exception block. What's better is that you can even specify the exception.
Adding this to your code would look something like:
for fpath in list:
if (fpath.endswith(".m4v")):
cdir=os.path.dirname(fpath)
os.chdir(cdir)
filename=os.path.basename(fpath)
try:
os.system("ffmpeg -i {0} temp_name.wav".format(filename))
except UnicodeEncodeError:
print("Some failure message.. Continuing to next..")
# os.remove(filename)
continue # This skips the rest of the current iteration and jumps to the top of the loop.
ofnamepath=os.path.splitext(fpath)[0]
temp_name=os.path.join(cdir, "temp_name.wav")
new_name = os.path.join(ofnamepath+'.wav')
os.rename(temp_name,new_name)
old_name=os.path.join(ofnamepath+'.m4v')
os.remove(old_name)
Uncomment the # os.remove(filename) to have your files deleted. Are you sure you want to permanently delete them?
I have a long list of audio files, and some of them are longer than an hour. I am using Jupyter notebook, Python 3.6 and TinyTag library to get a duration of audio. My code below goes over the files and if a file is longer than an hour, it splits the file into one-hour long pieces, and a leftover piece less than an hour, and copies the pieces as fname_1,fname_2, etc. The code was working for the previous datasets I tried, but this time after running for a while, I get the error below. I don`t know where this is coming from and how to fix it, I have already read the similar titled questions but their contents were different. Thanks in advance.
# fpaths is the list of filepaths
for i in range(0,len(fpaths)):
fpath=fpaths[i]
fname=os.path.basename(fpath)
fname0=os.path.splitext(fname)[0] #name without extension
tag = TinyTag.get(fname)
if tag.duration > 3600:
cmd2 = "ffmpeg -i %s -f segment -segment_time 3600 -c copy %s" %(fpath, fname0) + "_%d.wav"
os.system(cmd2)
os.remove(fpath)
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-10-79d0ceebf75d> in <module>()
7 fname0=os.path.splitext(fname)[0]
8 tag = TinyTag.get(fname)
----> 9 if tag.duration > 3600:
10 cmd2 = "ffmpeg -i %s -f segment -segment_time 3600 -c copy %s" %(fpath, fname0) + "_%d.wav"
11 os.system(cmd2)
TypeError: '>' not supported between instances of 'NoneType' and 'int'
Seems like some of those results do not have a duration
Perhaps change it to:
if tag.duration and tag.duration > 3600:
.....