Using 'with open(...) as ...' together with configparser.ConfigParser.read

Post by Loris Bennett
Hi,
With Python 3.9.18, if I do
config = configparser.ConfigParser()
config.read(config_file)
print(config.sections())
i.e try to read the configuration with the variable defined via 'with
... as', I get
[]
whereas if I use the file name directly
config = configparser.ConfigParser()
config.read(args.config_file)
print(config.sections())
I get
['loggers', 'handlers', 'formatters', 'logger_root', 'handler_fileHandler', 'handler_consoleHandler', 'formatter_defaultFormatter']
which is what I expect.
If I print type of 'config_file' I get
<class '_io.TextIOWrapper'>
whereas 'args.config_file' is just
<class 'str'>
Should I be able to use the '_io.TextIOWrapper' object variable here? If so how?
Here
https://docs.python.org/3.9/library/configparser.html
there are examples which use the 'with open ... as' variable for writing
a configuration file, but not for reading one.

As per the docs you link to, the read() method only takes filename(s)
as arguments, if you have an already-open file you want to read then
you should use the read_file() method instead.

Loris Bennett

2024-10-30 13:03:55 UTC

As per the docs you link to, the read() method only takes filename(s)
as arguments, if you have an already-open file you want to read then
you should use the read_file() method instead.

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.

However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

Cheers,

Loris

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Jon Ribbens

2024-10-30 15:41:13 UTC

Post by Jon Ribbens
As per the docs you link to, the read() method only takes filename(s)
as arguments, if you have an already-open file you want to read then
you should use the read_file() method instead.

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.
However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

The ConfigParser module provides read(), read_file(), read_string(),
and read_dict() methods. I think they were just trying to be
comprehensive. It's a bit non-Pythonic really.

Loris Bennett

2024-10-30 15:57:44 UTC

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.
However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

The ConfigParser module provides read(), read_file(), read_string(),
and read_dict() methods. I think they were just trying to be
comprehensive. It's a bit non-Pythonic really.

OK, but is there a common situation might I be obliged to use
'read_file'? I.e. is there some common case where the file name is not
available, only a corresponding file-like object or stream?

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Jon Ribbens

2024-10-30 17:57:23 UTC

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.
However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

The ConfigParser module provides read(), read_file(), read_string(),
and read_dict() methods. I think they were just trying to be
comprehensive. It's a bit non-Pythonic really.

OK, but is there a common situation might I be obliged to use
'read_file'? I.e. is there some common case where the file name is not
available, only a corresponding file-like object or stream?

Well, sure - any time it's not being read from a file. A bit ironic
that the method to use in that situation is "read_file", of course.
In my view the read() and read_file() methods have their names the
wrong way round. But bear in mind this code is 27 years old, and
the read() function came first.

Loris Bennett

2024-10-31 06:47:17 UTC

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.
However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

The ConfigParser module provides read(), read_file(), read_string(),
and read_dict() methods. I think they were just trying to be
comprehensive. It's a bit non-Pythonic really.

OK, but is there a common situation might I be obliged to use
'read_file'? I.e. is there some common case where the file name is not
available, only a corresponding file-like object or stream?

Yes, I suppose history has a lot to answer for :-)

However I didn't make myself clear: I understand that there are
different functions, depending on whether I have a file name or a
stream. Nevertheless, I just can't think of a practical example where I
might just have *only* a stream, especially one containing my
configuration data. I was just interested to know if anyone can give an
example.

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Jon Ribbens

2024-10-31 08:41:22 UTC

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.
However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

The ConfigParser module provides read(), read_file(), read_string(),
and read_dict() methods. I think they were just trying to be
comprehensive. It's a bit non-Pythonic really.

OK, but is there a common situation might I be obliged to use
'read_file'? I.e. is there some common case where the file name is not
available, only a corresponding file-like object or stream?

Yes, I suppose history has a lot to answer for :-)
However I didn't make myself clear: I understand that there are
different functions, depending on whether I have a file name or a
stream. Nevertheless, I just can't think of a practical example where I
might just have *only* a stream, especially one containing my
configuration data. I was just interested to know if anyone can give an
example.

That was answered the first sentence of my reply. It's a bit vague
because in most of the situations I can think of, one of the other
read_*() methods would probably be more appropriate. But again,
the history is that read_file() was added first (originally called
readfp() ) so it had to handle all cases where the data being read
was not coming from a named filesystem file - e.g. it's coming over
a Unix socket, or an HTTP request, or from a database.

It is good practice in general to provide a method that allows your
class to read data as a stream, if that is appropriate for what
you're doing, so that people aren't unnecessarily forced to load
data fully into memory or write it to a file, as well as perhaps a
convenience method thaat will read from a named file for people who
are doing that.

Karsten Hilbert

2024-10-31 16:10:42 UTC

Post by Loris Bennett
However I didn't make myself clear: I understand that there are
different functions, depending on whether I have a file name or a
stream. Nevertheless, I just can't think of a practical example where I
might just have *only* a stream, especially one containing my
configuration data. I was just interested to know if anyone can give an
example.

Apart from the fact that any data source can be made into a
file: one might have a stream of data coming in over, say,
http, as in a centralized configuration repository.

Karsten
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MRAB

2024-10-31 17:06:11 UTC

As you and others have pointed out, this is indeed covered in the docs,
so mea culpa.
However, whereas I can see why you might want to read the config from a
dict or a string, what would be a use case in which I would want to
read from an open file rather than just reading from a file(name)?

The ConfigParser module provides read(), read_file(), read_string(),
and read_dict() methods. I think they were just trying to be
comprehensive. It's a bit non-Pythonic really.

OK, but is there a common situation might I be obliged to use
'read_file'? I.e. is there some common case where the file name is not
available, only a corresponding file-like object or stream?

Yes, I suppose history has a lot to answer for :-)
However I didn't make myself clear: I understand that there are
different functions, depending on whether I have a file name or a
stream. Nevertheless, I just can't think of a practical example where I
might just have *only* a stream, especially one containing my
configuration data. I was just interested to know if anyone can give an
example.

What if the config file was inside a zipped folder?

Although I haven't used ConfigParser like that, I have read the contents
of files that are in a zipped folder. It means that I don't have to
extract the file first.

MRAB

2024-10-29 16:10:47 UTC

'config.read' expects a path or paths. If you give it a file handle, it
treats it as an iterable. (It might be reading the line as paths of
files, but I haven't tested it).

If you want to read from an open file, use 'config.read_file' instead.

Lawrence D'Oliveiro

2024-10-30 00:10:14 UTC