ValueError: embedded null byte when opening a file using bytestring Python

Question

I try to open a file (here bytestring is shortened) but get ValueError: embedded null byte

My code:

file = b'\x03\x04\x14\x00'

with open(file) as f:
    print(f.name)

I get this:

ValueError: embedded null byte

It's not the whole bytestring, original bytestring is super long because it's an excel file and it has hundreds of null bytes — Eugene Levy
– Eugene Levy, Commented Jul 21, 2021 at 11:54
So this bytestring isn't a file name? Why are you using open on it at all? Are you trying to pass the actual bytes contained in the file? This sounds like an XY problem. What are you trying to do? — John Coleman
– John Coleman, Commented Jul 21, 2021 at 11:59
I'm sending a file in bytes format to a server, server receives a file (bytes) and should extract the file name. One of the options is to use this: with open(bytes) as f: name = f.name — Eugene Levy
– Eugene Levy, Commented Jul 21, 2021 at 12:06
Perhaps you could try mode = 'rb' in open, though if these bytes are the whole file rather than the name of the file, I don't think it really makes sense. — John Coleman
– John Coleman, Commented Jul 21, 2021 at 12:26

Sean McCarthy · Accepted Answer · 2022-04-28 16:57:54Z

5

Here's your code; let's go through it. I see three issues.

file = b'\x03\x04\x14\x00'

with open(file) as f:
    print(f.name)

The open(file) requires a filename or path, not bytes.
Your file is actually the bytes you'd get from running f.read(), after opening the file.
Finally, in f.name, the "name" is probably a "property" of a file Path (i.e. from pathlib import Path).

Typically, the pattern would look more like this:

from pathlib import Path

file = Path("/home/user/docs/spreadsheet.csv")
print(file.name)

# Open file in "read-binary" mode, and read all the content into the "bytes_" variable
with open(file, 'rb') as f:
    bytes_ = f.read()

print(bytes_)

answered Apr 28, 2022 at 16:57

Sean McCarthy

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