nanoutils.file_container¶

An abstract container for reading and writing files.

Index¶

`file_to_context`(file, **kwargs)	Take a path- or file-like object and return an appropiate context manager.
`AbstractFileContainer`(args, *kwargs)	An abstract container for reading and writing files.

API¶

nanoutils.file_to_context(file, **kwargs)[source]¶

Take a path- or file-like object and return an appropiate context manager.

Passing a path-like object will supply it to open(), while passing a file-like object will pass it to contextlib.nullcontext().

Examples

>>> from io import StringIO
>>> from nanoutils import file_to_context

>>> path_like = 'file_name.txt'
>>> file_like = StringIO('this is a file-like object')

>>> context1 = file_to_context(file_like)
>>> with context1 as f1:
...     ...  

>>> context2 = file_to_context(path_like)  
>>> with context2 as f2:  
...     ... # insert operations here  

Parameters:

file (str, bytes, os.PathLike or IO) – A path- or file-like object.
**kwargs (Any) – Further keyword arguments for open(). Only relevant if file is a path-like object.

Returns:

An initialized context manager. Entering the context manager will return a file-like object.

Return type:

ContextManager[IO]

class nanoutils.AbstractFileContainer(*args, **kwargs)[source]¶

An abstract container for reading and writing files.

Two public methods are defined within this class:

AbstractFileContainer.read(): Construct a new instance from this object’s class by reading the content to a file or file object. How the content of the to-be read file is parsed has to be defined in the AbstractFileContainer._read() abstract method. Additional post processing, after the new instance has been created, can be performed with AbstractFileContainer._read_postprocess()
AbstractFileContainer.write(): Write the content of this instance to an opened file or file object. How the content of the to-be exported class instance is parsed has to be defined in the AbstractFileContainer._write()

Examples

>>> from io import StringIO
>>> from nanoutils import AbstractFileContainer

>>> class SubClass(AbstractFileContainer):
...     def __init__(self, value: str):
...         self.value = value
...
...     @classmethod
...     def _read(cls, file_obj, decoder):
...         value = decoder(file_obj.read())
...         return {'value': value}
...
...     def _write(self, file_obj, encoder):
...         value = encoder(self.value)
...         file_obj.write(value)

>>> file1 = StringIO('This is a file-like object')
>>> file2 = StringIO()

>>> obj = SubClass.read(file1)
>>> obj.write(file2)

>>> print(file2.getvalue())
This is a file-like object

classmethod read(file, bytes_decoding=None, **kwargs)[source]¶

Construct a new instance from this object’s class by reading the content of file.

Parameters:

file (str, bytes, os.PathLike or IO) –
A path- or file-like object.
bytes_decoding (str, optional) – The type of encoding to use when reading from file when it will be/is be opened in bytes mode. This value should be left empty otherwise.
**kwargs (Any) – Further keyword arguments for open(). Only relevant if file is a path-like object.

Returns:

A new instance constructed from file.

Return type:

nanoutils.AbstractFileContainer

abstract classmethod _read(file_obj, decoder)[source]¶

A helper function for read().

Parameters:

file_obj (IO[AnyStr]) – A file-like object opened in read mode.
decoder (Callable[[AnyStr], str]) – A function for converting the items of file_obj into strings.

Returns:

A dictionary with keyword arguments for a new instance of this objects’ class.

Return type:

Dict[str, Any]