"""
FileIO: Module for reading and writing various file types in a Pythonic way.
This module should not be used directly, instead...
```
import pysal.core.FileIO as FileIO
```
Readers and Writers will mimic python file objects.
.seek(n) seeks to the n'th object
.read(n) reads n objects, default == all
.next() reads the next object
"""
# ruff: noqa: ARG002, N801, N802, N803, N806, SIM115
__author__ = "Charles R Schmidt <schmidtc@gmail.com>"
__all__ = ["FileIO"]
import os.path
from warnings import warn
from ..common import MISSINGVALUE
class FileIO_MetaCls(type):
"""This meta class is instantiated when the class is first defined. All
subclasses of `FileIO` also inherit this meta class, which registers
their abilities with the FileIO registry. Subclasses must contain
``FORMATS`` and ``MODES`` (both are ``type(list)``).
Raises
------
TypeError
FileIO subclasses must have ``FORMATS`` and ``MODES`` defined.
"""
def __new__(cls, name, bases, dict_):
cls = type.__new__(cls, name, bases, dict_)
if name != "FileIO" and name != "DataTable":
if "FORMATS" in dict_ and "MODES" in dict_:
# msg = "Registering %s with FileIO.\n\tFormats: %r\n\tModes: %r"
# msg = msg % (name, dict["FORMATS"], dict["MODES"])
FileIO._register(cls, dict_["FORMATS"], dict_["MODES"])
else:
raise TypeError(
"FileIO subclasses must have 'FORMATS' and 'MODES' defined."
)
return cls
[docs]
class FileIO(metaclass=FileIO_MetaCls): # should be a type?
"""Metaclass for supporting spatial data file read and write.
How this works:
``FileIO.open(\\*args) == FileIO(\\*args)``
When creating a new instance of `FileIO` the ``.__new__`` method intercepts.
``.__new__`` parses the filename to determine the ``fileType``. Next,
``.__registry`` and checked for that type. Each type supports one or more modes
(``['r', 'w', 'a', etc.]``). If we support the type and mode, an instance of the
appropriate handler is created and returned. All handlers must inherit from this
class, and by doing so are automatically added to the ``.__registry`` and are
forced to conform to the prescribed API. The metaclass takes care of the
registration by parsing the class definition. It doesn't make much sense to
treat weights in the same way as shapefiles and dbfs, so...
* ... for now we'll just return an instance of `W` on ``mode='r'``.
* ... on ``mode='w'``, ``.write`` will expect an instance of `W`.
"""
__registry = {} # {'shp':{'r':[OGRshpReader,pysalShpReader]}}
def __new__(cls, dataPath="", mode="r", dataFormat=None):
"""Intercepts the instantiation of ``FileIO`` and dispatches
to the correct handler. If no suitable handler is found a
python file object is returned.
"""
if cls is FileIO:
try:
newCls = object.__new__(
cls.__registry[cls.getType(dataPath, mode, dataFormat)][mode][0]
)
except KeyError:
return open(dataPath, mode)
return newCls
else:
return object.__new__(cls)
[docs]
@staticmethod
def getType(dataPath: str, mode: str, dataFormat=None) -> str:
"""Parse the ``dataPath`` and return the data type."""
if dataFormat:
ext = dataFormat
else:
ext = os.path.splitext(dataPath)[1]
ext = ext.replace(".", "")
ext = ext.lower()
if ext == "txt":
with open(dataPath, mode) as f:
l1 = f.readline()
l2 = f.readline()
try:
n, k = l1.split(",")
n, k = int(n), int(k)
fields = l2.split(",")
assert len(fields) == k
return "geoda_txt"
except AssertionError:
return ext
return ext
@classmethod
def _register(cls, parser, formats, modes):
"""This method is called automatically via the Metaclass of `FileIO` subclasses
This should be private, but that hides it from the Metaclass.
"""
assert cls is FileIO
for format_ in formats:
if format_ not in cls.__registry:
cls.__registry[format_] = {}
for mode in modes:
if mode not in cls.__registry[format_]:
cls.__registry[format_][mode] = []
cls.__registry[format_][mode].append(parser)
# cls.check()
[docs]
@classmethod
def check(cls):
"""Prints the contents of the registry."""
print("PySAL File I/O understands the following file extensions:")
for key, val in list(cls.__registry.items()):
print(f"Ext: '.{key}', Modes: {list(val.keys())!r}")
[docs]
@classmethod
def open(cls, *args, **kwargs): # noqa: A001, A003
"""Alias for ``FileIO()``."""
return cls(*args, **kwargs)
class _By_Row:
def __init__(self, parent):
self.p = parent
def __repr__(self) -> str:
if not self.p.ids:
return "keys: range(0,n)"
else:
return "keys: " + list(self.p.ids.keys()).__repr__()
def __getitem__(self, key) -> list | str:
if isinstance(key, list):
r = []
if self.p.ids:
for k in key:
r.append(self.p.get(self.p.ids[k]))
else:
for k in key:
r.append(self.p.get(k))
return r
if self.p.ids:
return self.p.get(self.p.ids[key])
else:
return self.p.get(key)
__call__ = __getitem__
[docs]
def __init__(self, dataPath="", mode="r", dataFormat=None):
self.dataPath = dataPath
self.dataObj = ""
self.mode = mode
# pos Should ALWAYS be in the range 0,...,n
# for custom IDs set the ids property.
self.pos = 0
self.__ids = None # {'id':n}
self.__rIds = None
self.closed = False
self._spec = []
self.header = []
def __getitem__(self, key):
return self.by_row.__getitem__(key)
@property
def by_row(self):
return self._By_Row(self)
def __getIds(self):
return self.__ids
def __setIds(self, ids: list | (dict | None)):
"""Property method for ``.ids``. Takes a list of ids and maps then
to a 0-based index. Need to provide a method to set ID's based on
a ``fieldName`` preferably without reading the whole file.
Raises
------
AssertionError
Raised when IDs are not unique.
"""
if isinstance(ids, list):
try:
assert len(ids) == len(set(ids))
except AssertionError:
raise KeyError("IDs must be unique.") from None
# keys: ID values: i
self.__ids = {}
# keys: i values: ID
self.__rIds = {}
for i, id_ in enumerate(ids):
self.__ids[id] = i
self.__rIds[i] = id_
elif isinstance(ids, dict):
self.__ids = ids
self.__rIds = {}
for id_, n in list(ids.items()):
self.__rIds[n] = id_
elif not ids:
self.__ids = None
self.__rIds = None
ids = property(fget=__getIds, fset=__setIds)
@property
def rIds(self) -> dict | None:
return self.__rIds
def __iter__(self):
self.seek(0)
return self
@staticmethod
def _complain_ifclosed(closed):
"""From `StringIO`.
Raises
------
ValueError
Raised when a file is already closed.
"""
if closed:
raise ValueError("I/O operation on closed file.")
[docs]
def cast(self, key, typ):
"""Cast ``key`` as ``typ``.
Raises
------
TypeError
Raised when a cast object in not callable.
KeyError
Raised when a key is not present.
"""
if key in self.header:
if not self._spec:
self._spec = [lambda x: x for k in self.header]
if typ is None:
self._spec[self.header.index(key)] = lambda x: x
else:
try:
assert callable(typ)
self._spec[self.header.index(key)] = typ
except AssertionError:
raise TypeError("Cast objects must be callable.") from None
else:
raise KeyError("%s" % key)
def _cast(self, row) -> list:
"""
Raises
------
ValueError
Raised when a value could not be cast a particular type.
"""
if self._spec and row:
try:
return [f(v) for f, v in zip(self._spec, row, strict=True)]
except ValueError:
r = []
for f, v in zip(self._spec, row, strict=True):
try:
if not v and f != str:
raise ValueError
r.append(f(v))
except ValueError:
msg = "Value '%r' could not be cast to %s, "
msg += "value set to MISSINGVALUE."
msg = msg % (v, str(f))
warn(msg, RuntimeWarning, stacklevel=2)
r.append(MISSINGVALUE)
return r
else:
return row
def __next__(self) -> list:
"""A `FileIO` object is its own iterator, see `StringIO`.
Raises
------
StopIteration
Raised at the EOF.
"""
self._complain_ifclosed(self.closed)
r = self.__read()
if r is None:
raise StopIteration
return r
[docs]
def close(self):
"""Subclasses should clean themselves up and then call this method."""
if not self.closed:
self.closed = True
del self.dataObj, self.pos
[docs]
def get(self, n: int) -> list:
"""Seeks the file to ``n`` and returns ``n``. If ``.ids`` is set
``n`` should be an id, else, ``n`` should be an offset.
"""
prev_pos = self.tell()
self.seek(n)
obj = self.__read()
self.seek(prev_pos)
return obj
[docs]
def seek(self, n: int):
"""Seek the `FileObj` to the beginning of the ``n``'th record.
If IDs are set, seeks to the beginning of the record at ID, ``n``.
"""
self._complain_ifclosed(self.closed)
self.pos = n
[docs]
def tell(self) -> int:
"""Return ID (or offset) of next object."""
self._complain_ifclosed(self.closed)
return self.pos
[docs]
def read(self, n=-1) -> list | None:
"""Read at most ``n`` objects, less if read hits EOF.
If size is negative or omitted read all objects until EOF.
Returns ``None`` if EOF is reached before any objects.
Raises
------
StopIteration
Raised at the EOF.
"""
self._complain_ifclosed(self.closed)
if n < 0:
# return list(self)
result = []
while 1:
try:
result.append(self.__read())
except StopIteration:
break
return result
elif n == 0:
return None
else:
result = []
for _i in range(0, n):
try:
result.append(self.__read())
except StopIteration:
break
return result
def __read(self) -> list:
"""Gets one row from the file handler, and if necessary casts it's objects.
Raises
------
StopIteration
Raised at the EOF.
"""
row = self._read()
if row is None:
raise StopIteration
row = self._cast(row)
return row
def _read(self):
"""Must be implemented by subclasses that support 'r' subclasses.
Should increment ``.pos`` and redefine this doc string.
Raises
------
NotImplementedError
"""
self._complain_ifclosed(self.closed)
raise NotImplementedError
[docs]
def truncate(self, size=None):
"""Should be implemented by subclasses and redefine this doc string.
Raises
------
NotImplementedError
"""
self._complain_ifclosed(self.closed)
raise NotImplementedError
[docs]
def write(self, obj):
"""Must be implemented by subclasses that support 'w' subclasses
Should increment ``.pos``. Subclasses should also check if ``obj``
is an instance of type(list) and redefine this doc string.
Raises
------
NotImplementedError
"""
self._complain_ifclosed(self.closed)
"Write obj to dataObj"
raise NotImplementedError
[docs]
def flush(self):
"""
Raises
------
NotImplementedError
"""
self._complain_ifclosed(self.closed)
raise NotImplementedError