A pure Python library supporting Uniform eXchange Format, a plain text human readable optionally typed storage format.
Project description
Python UXF Library
UXF is a plain text human readable optionally typed storage format. UXF may serve as a convenient alternative to csv, ini, json, sqlite, toml, xml, or yaml.
For details of the Uniform eXchange Format (UXF) supported by this library, see the UXF Overview. (PyPI link to UXF Overview.)
Introduction
The Python uxf
library works out of the box with the standard library and
one dependency,
editabletuple. It
requires Python 3.8 or later.
- Install:
python3 -m pip install uxf
(or download the wheel.whl
files and dopython -m pip install uxf....whl editabletuple...whl
where ... varies) - Run:
python3 -m uxf -h
# this shows the command line help - Use:
import uxf
# see theuxf.py
module docs and API for the API
Using uxf
as an executable (e.g., python3 -m uxf ...
) provides a means
of doing .uxf
to .uxf
conversions (e.g., compress or uncompress or to
use the standard pretty print format). The executable can also be used for
linting, for deleting unused ttypes, and for replacing imports to ensure
that UXF files are stand-alone.
Installed alongside uxf.py
are uxflint.py
and uxfconvert.py
which
might prove useful to see how to use uxf
. For example, uxfconvert.py
can
losslessly convert .uxf
to .json
or .xml
and back. It can also do some
simple conversions to and from .csv
, to .ini
, and to and from .sqlite
,
but these are really to illustrate use of the uxf.py
APIs. And also see
the UXF test files in the ../testdata
folder, the Python examples in the
py/eg
folder, and the Python tests in the py/t
folder.
If you just want to create a small standalone .pyz
, you could simply copy
uxf.py
and editabletuple.py
into your project folder and include them in
your .pyz
file.
Python UXF Types
Most Python types convert losslessly to and from UXF types. In particular:
Python Type | UXF type | Notes |
---|---|---|
None |
null |
|
bool |
bool |
|
bytes |
bytes |
|
bytearray |
bytes |
Lossless conversion but type changes to Python bytes |
datetime.date |
date |
|
datetime.datetime |
datetime |
Loses any timezone and only preserves to the nearest 1-second |
int |
int |
|
float |
real |
|
str |
str |
|
uxf.List |
list |
|
uxf.Map |
map |
|
uxf.Table |
table |
A List is a Python collections.UserList
subclass with
.data
(the list), .comment
and .vtype
attributes. A .vtype
holds a
str
representing the name of the corresponding UXF type (e.g., int
,
real
, etc.) or a ttype
(the name of a custom table type; see
TClass). If a .vtype
is None
it means that any UXF
type may be stored.
Similarly a Map is a Python collections.UserDict
subclass
with .data
(the dict), .comment
, .ktype
, and .vtype
attributes. The
.ktype
is a str
like the .vtype
except that it may only be None
(accept any valid ktype) or one of bytes
, date
, datetime
, int
, or
str
. The .vtype
works just the same as for Lists.
The Table class has .records
, .comment
, and .tclass
attributes; with .tclass
holding a TClass which in turn
holds the table's ttype
(i.e., its table type name), and the table's field
names and (optional) types. In all cases a type of None
signifies that any
type valid for the context may be used.
Custom types can be represented using ttypes. For example, for points you
could define a ttype such as: =point x:real y:real
. Then you could
include single points like (point 1.5 7.2)
, or many of them such as
(point 1.5 7.2 8.3 -9.4 14.8 0.6)
.
Collection types such as set
, frozenset
, tuple
, or collections.deque
are automatically converted to a List when they are
encountered. Of course, these are one way conversions.
API
The simplest part of the API loads and saves (dumps) UXF data from/to strings or files.
Reading and Writing UXF Data
load(filename_or_filelike): -> uxo
loads(uxt): -> uxo
The load() function reads UXF data from a file or file-like
object, and the loads() function reads UXF data from a string.
These functions take several optional arguments; see load() and
loads(). The returned uxo
(UXF object) is of type
Uxf.
dump(filename_or_filelike, data)
dumps(data) -> uxt
The dump() function writes the data in UXF format to a file or
file-like object, and the dumps() function writes the data
into a string that's then returned (here called uxt
to indicate UXF text).
These functions take several optional arguments; see dump() and
dumps(). The data can be a Uxf object or a single
list
, List, dict
, Map, or
Table.
If the data contains values of types that aren't supported by UXF, they could be transformed in advance (e.g., to a custom table type, a ttype).
See also the examples in the py/eg
folder and the tests in the py/t
folder.
API Notes
A UXF object (called a uxo
in these docs) has a .value
attribute that is always a List or Map or
Table. The first two have essentially the same APIs as
list
and dict
respectively. The Table API is a little
similar to a list
. Individual records can be accessed (read and updated)
using table[row]
, and individual files using table[row][column]
or
table[row].fieldname
. For small tables, records can be accessed with the
first
, second
, third
, or fourth
properties. The best way to append
new records is to use the Table's append()
method.
The uxf
module distinguishes between a ttype (the name of a user-defined
table) and a TClass (the Python class which represents a
user-defined table). A TClass has .ttype
and .fields
attributes.
For reading UXF data it is easiest to iterate, and to do so recursively, if
the data has nested collections. Note that the visit.py
example provides a
way of doing this using the visitor design pattern. The uxfconvert.py
example shows alternative approaches to manual iteration.
Note that for imports, if the filename is relative it is searched for in the
same folder as the importing UXF file, and if not found there, in the
current folder, and if not there either, in each of the paths in UXF_PATH
(if any).
Note that the __version__
is the module version (i.e., the version of this
implementation), while the VERSION
is the maximum UXF version that this
module can read (and the UXF version that it writes).
Classes
The classes are documented in convenience order. Here are alphabetically ordered links: Error, Field, Format, List, Map, Table, TClass, Uxf.
Uxf
A Uxf
object represents a UXF file in memory.
The easiest way to obtain a Uxf
object is to use one of the module-level
functions, load() or loads(). Of course, you can
also create Uxf
s programatically (as shown in many of the examples and
tests).
Constructor
Uxf(value=None, *, custom='', tclasses=None, comment=None)
The Uxf
constructor takes an optional value
(a list
, List
, tuple
,
dict
, Map
, or Table
) and optional (by keyword arguments) custom
string, tclasses
(a dict
whose names are ttypes and whose values are
the corresponding TClasses), and comment
string.
To create a Uxf
programmatically (rather than by using, say,
load(), you can either create it empty, or with some data and
optionally, some ttypes.
value = ... # a list, uxf.List, dict, uxf.Map, or uxf.Table
point_ttype = uxf.TClass('point', (uxf.Field('x', 'real'), uxf.Field('y', 'real')))
uxo = uxf.Uxf(value, tclasses={point_ttype.ttype: point_ttype})
An alternative is to do this:
uxo = uxf.loads('uxf 1.0\n=point x:real y:real\n[]')
uxo.value = value
Properties
.value
A List, Map, or Table. Since
these classes can nest, a Uxf
can represent any arbitrary data structure.
.custom
An opional str
used for customizing the file format, i.e., the header text
that follows the initial uxf 1.0
on the first line.
.tclasses
A possibly empty dict
where each key is a ttype
(i.e., the
.tclass.ttype
which is a TClass's name—a str
) and each
value is a TClass object.
.comment
An optional file-level str
.
.imports
A possibly empty dict
where each key is a ttype
and where each value is
a str
holding that type's import text.
.import_filenames
A utility property useful for some UXF processors. It yields all the unique import filenames.
Methods
.load(filename_or_filelike, *, on_error=on_error, drop_unused=False, replace_imports=False)
Convenience method that wraps the module-level load() function.
.loads(uxt, filename='-', *, on_error=on_error, drop_unused=False, replace_imports=False)
Convenience method that wraps the module-level loads() function.
.dump(filename_or_filelike, *, on_error=on_error, format=Format())
Convenience method that wraps the module-level dump() function.
.dumps(*, on_error=on_error, format=Format())
Convenience method that wraps the module-level dumps() function.
List
A class used to represent a UXF list. It is a collections.UserList
subclass which holds its list in the .data
attribute and that also has
.comment
and .vtype
attributes.
Constructor
List(seq=None, *, vtype=None, comment=None)
The seq
can be a list
, tuple
, or any iterable acceptable to the
built-in list()
type. The vtype is a str
signifying the type of value
this list may hold; None
means values may be of any UXF-compatible type
(see Python UXF Types). A str
may be passed as the
comment
.
See Python UXF Types for more about vtypes.
Map
A class used to represent a UXF map. It is a collections.UserDict
subclass
that holds its dict in the .data
attribute and that also has .comment
,
.ktype
, and .vtype
attributes.
Constructor
Map(d=None, *, ktype=None, vtype=None, comment=None)
The d
can be a dict
or any single value acceptable to the built-in
dict()
type. The ktype is a str
signifying the type of key that must
be used; None
means that any valid ktype, i.e., 'bytes'
, 'date'
,
'datetime'
, 'int'
, or 'str'
. The vtype is a str
signifying the
type of value this Map
may hold; None
means values may be of any
UXF-compatible type (see Python UXF Types). A str
may
be passed as the comment
.
See Python UXF Types for more about ktypes and vtypes.
Table
A class used to store UXF Tables.
Constructor
Table(tclass=None, *, records=None, comment=None)
A Table
can be created using the constructor, passing a
TClass, and optionally, records (a list of lists, where
each sublist has len(tclass.fields)
values), and a comment (a str
).
Alternativvely, use the table() convenience function which
takes a ttype (a str
), and fields.
See Python UXF Types for more about and ttypes.
Properties
.tclass
A TClass which holds the table's ttype and field names (and optional field types).
.ttype
A convenience for .tclass.ttype
.
.records
The table's data: a list of values where each value is either a list with
len(table.fields)
values, or an
editabletuple of type
.RecordClass
.
.RecordClass
The table's record class, a dynamically created
editabletuple, which
can be used to create a single record by calling it with each of the
record's fields' values (or with *sequence
where len(sequence)
equals
the number of fields). When a table record is accessed (e.g., when one row
of the table's list is returned), it is returned as an instance of this
class.
.fields
A convenience for .tclass.fields
.
.first
The table's first record as a RecordClass
editabletuple, or
None
if the table is empty.
.second
The table's second record or None
.
.third
The table's third record or None
.
.fourth
The table's fourth record or None
.
.last
The table's last record or None
.
.is_scalar
This is True
if all the table's values are (or ought to be given its
fields' types) scalars; otherwise it is False
. Its main use is as a helper
for the dump() and dumps() functions.
Operators
table[row]
The table's row
-th record as a RecordClass
editabletuple. The
returned record is editable, so to get or set a field use
table[row][column]
or table[row].fieldname
.
To replace an entire record, use table[row] = record
where record
is a
sequence (e.g., a tuple
of length len(table.fields)
), or a
table.RecordClass
instance. (See also append()
below.)
To delete an entire record, use del table[row]
.
iter(table)
For example, for record in table:
. Yields every record in the table as a
RecordClass
instance.
len(table)
The number of records (rows) in the table.
Methods
.append(record)
Appends a new row to the table's list of lists as an
editabletuple of type
.RecordClass
. The row can be provided as a RecordClass
editabletuple or
as a sequence of field values (which will then be converted to the table's
RecordClass
).
.insert(index, record)
Inserts the given record (or sequence of field values which is converted to
a RecordClass
instance) into the table at the given index
position.
.field(column)
This function is a convenience for .tclass.fields[column]
.
TClass
This class is used to store a Table's ttype (i.e., its name) and fields.
Constructor
TClass(ttype, fields=None, *, comment=None)
The ttype
must be a str
that holds the TClass
's name (equivalent to
a vtype or ktype name); it may not be the same as a built-in type name
or constant. Leave fields
as None
for a fieldless table; otherwise pass
a sequence of field names (str
's) or Field
's (which have field names
and optionally types). The .comment
may be passed a str
.
The .ttype
attribute holds the TClass
's name. The .fields
attribute
holds a list of fields of type Field. The .comment
holds
an optional str
.
The .isfieldless
property returns True
if there are no fields (which is
valid for a fieldless table); otherwise returns False
.
Field
This class is used to store a TClass's fields, i.e., the fields for a Table.
Constructor
Field(name, vtype=None)
The name
must start with a letter and be followed by
0-uxf.MAX_IDENTIFIER_LEN-1
letters, digits, or underscores; it may not be
the same as a built-in type name or constant. A vtype of None
means that
the field may hold any valid UXF type (see Python UXF
Types); otherwise it must be one of these str
s:
'bool'
, 'bytes'
, 'date'
, 'datetime'
, 'int'
, 'real'
, 'list'
,
'map'
, 'str'
, or 'table'
; or a ttype name.
Format
This class is used to specify aspects of the output format for the dump() and dumps() functions (and the equivalent methods).
Constructor
Format(indent=' ', wrap_width=96, realdp=None, max_short_len=32)
The dump() and dumps() functions use the default
Format()
which uses the defaults shown (indent is two spaces). However, by
creating and passing your own Format
object, you can change these to suit
your needs. For realdp
, None
signifies use however many digits after the
decimal point are needed for UXF real
's (i.e., for Python float
's);
otherwise specify a value 0-15.
For example, if you had a Uxf
object with a table and wanted the output to
be one record per line, with real
s output with 3 decimal places, you
could pass a format of Format(wrap_width=None, realdp=3)
.
Error
This class is used to propagate errors.
(If this module produces an exception that isn't a uxf.Error
or OSError
subclass then it is probably a bug that should be reported.)
Functions
The functions are documented in convenience order. Here are alphabetically ordered links: append_to_parent(), canonicalize(), dump(), dumps(), isoformat(), isasciidigit(), is_scalar(), load(), loads(), naturalize(), on_error(), table().
load(filename_or_filelike, *, on_error=on_error, drop_unused=False, replace_imports=False)
Returns a Uxf object.
filename_or_filelike
is sys.stdin
or a filename (str
or
pathlib.Path
) or an open readable file (text mode UTF-8 encoded,
optionally gzipped).
on_error
is a custom error handling function that defaults to
on_error.
If drop_unused
is True
, then any ttype definitions in the file that
aren't actually used in the data are dropped. So if the Uxf
is later
dumped, the dropped ttype definitions will not be present.
If replace_imports
is True
, then any imports are replaced by the ttype
definitions that they import. So if the Uxf
is later dumped, no imports
will be present; instead any imported ttypes will be dumped as ttype
definitions. Normally, if you use replace_imports=True
, then you would
also use drop_unused=True
.
loads(uxt, filename='-', *, on_error=on_error, drop_unused=False, replace_imports=False)
Returns a Uxf object.
uxt
must be a str
of UXF data, e.g., uxf 1.0\n[1 2 3]
.
If given, the filename
is used for error messages.
For more on the other argument see load().
dump(filename_or_filelike, data, *, on_error=on_error, format=Format())
filename_or_filelike
is sys.stdout
or a filename or an open writable
file (text mode UTF-8 encoded). If filename_or_filelike
is a filename with
a .gz
suffix then the output will be gzip-compressed.
data
is a Uxf object, or a list, List, dict,
Map, or Table, that this function will write
to the filename_or_filelike
in UXF format.
format
specifies aspects of the output (e.g., indent); see the
Format class for details.
dumps(data, *, on_error=on_error, format=Format())
data
is a Uxf object, or a list, List, dict,
Map, or Table that this function will write to
a str
in UXF format which will then be returned.
For more on the other arguments see dump().
table(ttype, fields, *, comment=None)
Convenience function for creating empty tables with a new TClass.
See also the Table constructor.
on_error(lino, code, message, *, filename, fail=False, verbose=True)
This is the default error handler which you can replace by passing a custom one to load(), loads(), dump(), or dumps().
This is called with the line number (lino), error code, error message, and
filename. The filename may be '-' or empty if the UXF is created in memory
rather than loaded from a file. If fail is True
it means the error is
unrecoverable, so the normal action would be to raise. If verbose is True
the normal action is to print a textual version of the error data to
stderr
.
To make on_error()
quieter:
on_error = functools.partial(uxf.on_error, verbose=False)
To make all errors fatal:
on_error = functools.partial(uxf.on_error, fail=True, verbose=False)
For further examples of custom on_error()
functions, see
t/test_errors.py
, t/test_imports.py
t/test_include.py
,
t/test_merge.py
, and t/test_sqlite.py
.
Returns True
if s
matches /^[0-9]+$/
. (Python's str.isdigit()
and
str.isdecimal()
both match additional Unicode digit characters which is
why we use isasciidigit()
.)
If dt
is a date
, returns the corresponding str
with format
'YYYY-MM-DD'
; if dt
is a datetime
, returns the corresponding str
with format 'YYYY-MM-DDTHH:MM:SS'
.
Given str
s
returns True
if the str
is 't', 'true', 'y', 'yes', or
False
if the str
is 'f', 'false', 'n', 'no' (case-insensitive); or
returns an int
if s
holds a parsable int, or a float
if s
holds a
parsable float
, or a datetime.datetime
if s
holds a parsable ISO8601
datetime, or a datetime.date
if s
holds a parsable ISO8601 date, or
failing these returns the original str
, s
, unchanged.
This is provided as a helper function (e.g., it is used by uxfconvert.py
).
Returns True
if x
is None
or a bool
, bytes
, bytearray
,
datetime.date
, datetime.datetime
, int
, float
, or str
; otherwise
returns False
. Its main use is as a helper for the dump() and
dumps() functions.
canonicalize(name, is_table_name)
Utility for UXF processors. Given a name
, returns a name
that is a valid
table or field name. See uxfconvert.py
for uses.
append_to_parent(parent, value)
Utility for UXF processors; see uxf.py
and uxfconvert.py
for examples of
use.
Constants
Constant | Description |
---|---|
VERSION |
The UXF file format version. |
RESERVED_WORDS |
A set of names that cannot be used for table or field names. |
UTF8 |
The string 'utf-8' . |
Command Line Usage
The uxf module can be used as an executable. To see the command line help run:
python3 -m uxf -h
or
path/to/uxf.py -h
Changes
- 1.1.0 Dropped
Format
'smax_fields_in_line
andmax_list_in_line
settings since neither worked: usewrap_width
instead. - 1.0.2 Bug fix: I missed a corner case in the previous fix; now fixed.
- 1.0.1 Bug fix: when
dump()
anddumps()
output ttype definitions, they now respect the format'swrap_width
andindent
settings. - 1.0.0 First stable release.
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