Python Valueerror: Embedded Null Byte When Reading Png File from Bash Pipe

Python ValueError: embedded null byte when reading png file from bash pipe

Try first to load raw data into a BytesIO container:

from io import BytesIO
from PIL import Image
from subprocess import Popen, PIPE

data = Popen.communicate(Popen(['import','-w','0x02a00001','png:-'], stdout=PIPE))[0]
scr = Image.open(BytesIO(data))

Mysterious embedded null byte error

• One of the AppConfig objects has null byte in its path attribute.
• One of the LOCALE_PATHS has null byte.
• One of the files is in the "wrong" encoding, so Django treats something has null byte (e. g. AppConfig.path).
• One of the files or directories in project directory has null byte (\x00) in its name.
• Other reason.

autoreload.py lines related to this issue. os.path.isdir() raises ValueError: embedded null byte if its argument has null byte, e. g. os.path.isdir('foo\x00bar').

You can try to edit autoreload.py, comment out these lines temporarily:

basedirs = [os.path.abspath(basedir) for basedir in basedirs
            if os.path.isdir(basedir)]

and add this:

temp_basedirs = []
for basedir in basedirs:
    try:
        if os.path.isdir(basedir):
            temp_basedirs.append(os.path.abspath(basedir))
    except ValueError:
        print(basedir)
        raise
basedirs = temp_basedirs

Find number of concurrent users in a SQL records

Clearly the number of concurrent users only changes when a user either starts or ends a period, so it is enough to determine the number of concurrent users during starts and ends. So, reusing test data provided by Remus (thank you Remus):

DECLARE @Table TABLE 
(
  UserId int, 
  StartedOn datetime,
  EndedOn datetime
);

insert into @table (UserId, startedOn, EndedOn)
select 1, '2009-7-12 14:01', '2009-7-12 15:01'
union all select 2, '2009-7-12 14:30', '2009-7-12 14:45'
union all select 3, '2009-7-12 14:47', '2009-7-12 15:30'
union all select 4, '2009-7-12 13:01', '2009-7-12 17:01'
union all select 5, '2009-7-12 14:15', '2009-7-12 18:01'
union all select 6, '2009-7-12 11:01', '2009-7-12 19:01'
union all select 1, '2009-7-12 16:07', '2009-7-12 19:01';

SELECT MAX(ConcurrentUsers) FROM(
SELECT COUNT(*) AS ConcurrentUsers FROM @table AS Sessions 
JOIN 
(SELECT DISTINCT StartedOn AS ChangeTime FROM @table
) AS ChangeTimes
ON ChangeTime >= StartedOn AND ChangeTime < EndedOn 
GROUP BY ChangeTime
) AS ConcurrencyAtChangeTimes
-------
5

BTW using DISTINCT per se is not a mistake - only abusing DISTINCT is. DISTINCT is just a tool, using it in this context is perfectly correct.

Edit: I was answering the OP's question: "how one could calculate this using T-SQL only".
Note that the question does not mention performance.

If the questions was this: "what is the fastest way to determine maximum concurrency if the data is stored in SQL Server", I would provide a different answer, something like this:

Consider the following alternatives

1. Write a cursor
2. Write a CLR cursor
3. Write a loop on the client
4. Use an RDBMS with decent cursors, such as Oracle or PostgreSql
5. For top performance, design your table differently, so that you can retrieve the answer in one index seek. This is what I do in my system if I need to deliver best possible performance.

If the question was "what is the fastest way to determine maximum concurrency using a T-SQL query", I would probably not answer at all. The reason: if I needed really good performance, I would not solve this problem in a T-SQL query.

Line contains NULL byte in CSV reader (Python)

I've solved a similar problem with an easier solution:

import codecs
csvReader = csv.reader(codecs.open('file.csv', 'rU', 'utf-16'))

The key was using the codecs module to open the file with the UTF-16 encoding, there are a lot more of encodings, check the documentation.

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