Examples¶
Validate with Pydantic¶
This example shows how to use pydantic to validate and parse a NestedText file. The file in this case specifies deployment settings for a web server:
debug: false
secret_key: t=)40**y&883y9gdpuw%aiig+wtc033(ui@^1ur72w#zhw3_ch
allowed_hosts:
- www.example.com
database:
engine: django.db.backends.mysql
host: db.example.com
port: 3306
user: www
webmaster_email: admin@example.com
Below is the code to parse this file. Note that basic types like integers, strings, Booleans, and lists are specified using standard type annotations. Dictionaries with specific keys are represented by model classes, and it is possible to reference one model from within another. Pydantic also has built-in support for validating email addresses, which we can take advantage of here:
#!/usr/bin/env python3
import nestedtext as nt
from pydantic import BaseModel, EmailStr
from typing import List
from pprint import pprint
class Database(BaseModel):
engine: str
host: str
port: int
user: str
class Config(BaseModel):
debug: bool
secret_key: str
allowed_hosts: List[str]
database: Database
webmaster_email: EmailStr
obj = nt.load('deploy.nt')
config = Config.parse_obj(obj)
pprint(config.dict())
This produces the following data structure:
{'allowed_hosts': ['www.example.com'],
'database': {'engine': 'django.db.backends.mysql',
'host': 'db.example.com',
'port': 3306,
'user': 'www'},
'debug': False,
'secret_key': 't=)40**y&883y9gdpuw%aiig+wtc033(ui@^1ur72w#zhw3_ch',
'webmaster_email': 'admin@example.com'}
Validate with Voluptuous¶
This example shows how to use voluptuous to validate and parse a NestedText
file and it demonstrates how to use the keymap argument from loads()
or
load()
to add location information to Voluptuous error messages.
The input file is the same as in the previous example, i.e. deployment settings for a web server:
debug: false
secret_key: t=)40**y&883y9gdpuw%aiig+wtc033(ui@^1ur72w#zhw3_ch
allowed_hosts:
- www.example.com
database:
engine: django.db.backends.mysql
host: db.example.com
port: 3306
user: www
webmaster_email: admin@example.com
Below is the code to parse this file. Note how the structure of the data is
specified using basic Python objects. The Coerce()
function is
necessary to have voluptuous convert string input to the given type; otherwise
it would simply check that the input matches the given type:
#!/usr/bin/env python3
import nestedtext as nt
from voluptuous import Schema, Coerce, MultipleInvalid
from inform import error, full_stop, terminate
from pprint import pprint
schema = Schema({
'debug': Coerce(bool),
'secret_key': str,
'allowed_hosts': [str],
'database': {
'engine': str,
'host': str,
'port': Coerce(int),
'user': str,
},
'webmaster_email': str,
})
try:
keymap = {}
raw = nt.load('deploy.nt', keymap=keymap)
config = schema(raw)
except nt.NestedTextError as e:
e.terminate()
except MultipleInvalid as e:
for err in e.errors:
kind = 'key' if 'key' in err.msg else 'value'
loc = keymap[tuple(err.path)]
error(full_stop(err.msg), culprit=err.path, codicil=loc.as_line(kind))
terminate()
pprint(config)
This produces the same result as in the previous example.
JSON to NestedText¶
This example implements a command-line utility that converts a JSON file to
NestedText. It demonstrates the use of dumps()
and
NestedTextError
.
#!/usr/bin/env python3
"""
Read a JSON file and convert it to NestedText.
usage:
json-to-nestedtext [options] [<filename>]
options:
-f, --force force overwrite of output file
-i <n>, --indent <n> number of spaces per indent [default: 4]
-w <n>, --width <n> desired maximum line width; specifying enables
use of single-line lists and dictionaries as long
as the fit in given width [default: 0]
If <filename> is not given, JSON input is taken from stdin and NestedText output
is written to stdout.
"""
from docopt import docopt
from inform import done, fatal, full_stop, os_error, warn
from pathlib import Path
import json
import nestedtext as nt
import sys
sys.stdin.reconfigure(encoding='utf-8')
sys.stdout.reconfigure(encoding='utf-8')
cmdline = docopt(__doc__)
input_filename = cmdline['<filename>']
try:
indent = int(cmdline['--indent'])
except Exception:
warn('expected positive integer for indent.', culprit=cmdline['--indent'])
indent = 4
try:
width = int(cmdline['--width'])
except Exception:
warn('expected non-negative integer for width.', culprit=cmdline['--width'])
width = 0
try:
# read JSON content; from file or from stdin
if input_filename:
input_path = Path(input_filename)
json_content = input_path.read_text(encoding='utf-8')
else:
json_content = sys.stdin.read()
data = json.loads(json_content)
# convert to NestedText
nestedtext_content = nt.dumps(data, indent=indent, width=width) + "\n"
# output NestedText content; to file or to stdout
if input_filename:
output_path = input_path.with_suffix('.nt')
if output_path.exists():
if not cmdline['--force']:
fatal('file exists, use -f to force over-write.', culprit=output_path)
output_path.write_text(nestedtext_content, encoding='utf-8')
else:
sys.stdout.write(nestedtext_content)
except OSError as e:
fatal(os_error(e))
except nt.NestedTextError as e:
e.terminate()
except KeyboardInterrupt:
done()
except json.JSONDecodeError as e:
# create a nice error message with surrounding context
msg = e.msg
culprit = input_filename
codicil = None
try:
lineno = e.lineno
culprit = (culprit, lineno)
colno = e.colno
lines_before = e.doc.split('\n')[lineno-2:lineno]
lines = []
for i, l in zip(range(lineno-len(lines_before), lineno), lines_before):
lines.append(f'{i+1:>4}> {l}')
lines_before = '\n'.join(lines)
lines_after = e.doc.split('\n')[lineno:lineno+1]
lines = []
for i, l in zip(range(lineno, lineno + len(lines_after)), lines_after):
lines.append(f'{i+1:>4}> {l}')
lines_after = '\n'.join(lines)
codicil = f"{lines_before}\n {colno*' '}△\n{lines_after}"
except Exception:
pass
fatal(full_stop(msg), culprit=culprit, codicil=codicil)
Be aware that not all JSON data can be converted to NestedText, and in the conversion much of the type information is lost.
json-to-nestedtext can be used as a JSON pretty printer:
> json-to-nestedtext < fumiko.json
treasurer:
name: Fumiko Purvis
address:
> 3636 Buffalo Ave
> Topeka, Kansas 20692
phone: 1-268-555-0280
email: fumiko.purvis@hotmail.com
additional roles:
- accounting task force
NestedText to JSON¶
This example implements a command-line utility that converts a NestedText file
to JSON. It demonstrates the use of load()
and
NestedTextError
.
#!/usr/bin/env python3
"""
Read a NestedText file and convert it to JSON.
usage:
nestedtext-to-json [options] [<filename>]
options:
-f, --force force overwrite of output file
-d, --dedup de-duplicate keys in dictionaries
If <filename> is not given, NestedText input is taken from stdin and JSON output
is written to stdout.
"""
from docopt import docopt
from inform import done, fatal, os_error
from pathlib import Path
import json
import nestedtext as nt
import sys
sys.stdin.reconfigure(encoding='utf-8')
sys.stdout.reconfigure(encoding='utf-8')
def de_dup(key, value, data, state):
if key not in state:
state[key] = 1
state[key] += 1
return f"{key}#{state[key]}"
cmdline = docopt(__doc__)
input_filename = cmdline['<filename>']
on_dup = de_dup if cmdline['--dedup'] else None
try:
if input_filename:
input_path = Path(input_filename)
data = nt.load(input_path, top='any', on_dup=de_dup)
json_content = json.dumps(data, indent=4, ensure_ascii=False)
output_path = input_path.with_suffix('.json')
if output_path.exists():
if not cmdline['--force']:
fatal('file exists, use -f to force over-write.', culprit=output_path)
output_path.write_text(json_content, encoding='utf-8')
else:
data = nt.load(sys.stdin, top='any', on_dup=de_dup)
json_content = json.dumps(data, indent=4, ensure_ascii=False)
sys.stdout.write(json_content + '\n')
except OSError as e:
fatal(os_error(e))
except nt.NestedTextError as e:
e.terminate()
except KeyboardInterrupt:
done()
CSV to NestedText¶
This example implements a command-line utility that converts a CSV file to
NestedText. It demonstrates the use of the converters argument to
dumps()
, which is used to cull empty dictionary fields.
#!/usr/bin/env python3
"""
Read a CSV file and convert it to NestedText.
usage:
csv-to-nestedtext [options] [<filename>]
options:
-n, --names first row contains column names
-c, --cull remove empty fields (only for --names)
-f, --force force overwrite of output file
-i <n>, --indent <n> number of spaces per indent [default: 4]
If <filename> is not given, csv input is taken from stdin and NestedText output
is written to stdout.
If --names is specified, then the first line is assumed to hold the column/field
names with the remaining lines containing the data. In this case the output is
a list of dictionaries. Otherwise every line contains data and that data is
output as a list of lists.
"""
from docopt import docopt
from inform import cull, done, fatal, full_stop, os_error, warn
from pathlib import Path
import csv
import nestedtext as nt
import sys
sys.stdin.reconfigure(encoding='utf-8')
sys.stdout.reconfigure(encoding='utf-8')
cmdline = docopt(__doc__)
input_filename = cmdline['<filename>']
try:
indent = int(cmdline['--indent'])
except Exception:
warn('expected positive integer for indent.', culprit=cmdline['--indent'])
indent = 4
# strip dictionaries of empty fields if requested
converters = {dict: cull} if cmdline['--cull'] else {}
try:
# read CSV content; from file or from stdin
if input_filename:
input_path = Path(input_filename)
csv_content = input_path.read_text(encoding='utf-8')
else:
csv_content = sys.stdin.read()
if cmdline['--names']:
data = csv.DictReader(csv_content.splitlines())
else:
data = csv.reader(csv_content.splitlines())
# convert to NestedText
nt_content = nt.dumps(data, indent=indent, converters=converters) + "\n"
# output NestedText content; to file or to stdout
if input_filename:
output_path = input_path.with_suffix('.nt')
if output_path.exists():
if not cmdline['--force']:
fatal('file exists, use -f to force over-write.', culprit=output_path)
output_path.write_text(nt_content, encoding='utf-8')
else:
sys.stdout.write(nt_content)
except OSError as e:
fatal(os_error(e))
except nt.NestedTextError as e:
e.terminate()
except csv.Error as e:
fatal(full_stop(e), culprit=(input_filename, data.line_num))
except KeyboardInterrupt:
done()
PyTest¶
This example highlights a PyTest package parametrize_from_file that allows you to neatly separate your test code from your test cases; the test cases being held in a NestedText file. Since test cases often contain code snippets, the ability of NestedText to hold arbitrary strings without the need for quoting or escaping results in very clean and simple test case specifications. Also, use of the eval function in the test code allows the fields in the test cases to be literal Python code.
The test cases:
# test_expr.nt
test_substitution:
-
given: first second
search: ^\s*(\w+)\s*(\w+)\s*$
replace: \2 \1
expected: second first
-
given: 4 * 7
search: ^\s*(\d+)\s*([-+*/])\s*(\d+)\s*$
replace: \1 \3 \2
expected: 4 7 *
test_expression:
-
given: 1 + 2
expected: 3
-
given: "1" + "2"
expected: "12"
-
given: pathlib.Path("/") / "tmp"
expected: pathlib.Path("/tmp")
And the corresponding test code:
# test_misc.py
import parametrize_from_file
import re
import pathlib
@parametrize_from_file
def test_substitution(given, search, replace, expected):
assert re.sub(search, replace, given) == expected
@parametrize_from_file
def test_expression(given, expected):
assert eval(given) == eval(expected)
Pretty Printing¶
Besides being a readable file format, NestedText makes a reasonable display format for structured data. This example further simplifies the output by stripping leading multiline string tags.
>>> import nestedtext as nt
>>> import re
>>>
>>> def pp(data):
... try:
... text = nt.dumps(data, default=repr)
... print(re.sub(r'^(\s*)[>:]\s?(.*)$', r'\1\2', text, flags=re.M))
... except nt.NestedTextError as e:
... e.report()
>>> addresses = nt.load('examples/address.nt')
>>> pp(addresses['Katheryn McDaniel'])
position: president
address:
138 Almond Street
Topeka, Kansas 20697
phone:
cell: 1-210-555-5297
home: 1-210-555-8470
email: KateMcD@aol.com
additional roles:
- board member
Normalizing keys¶
With data files created by non-programmers it is often desirable to allow
a certain amount of flexibility in the keys. For example, you may wish to
ignore case and be tolerant of extra spacing. However, the end applications
often needs the keys to be specific values. It is possible to normalize the
keys using a schema, but this can interfere with error reporting. Imagine there
is an error in the value associated with a set of keys, if the keys have been
changed by the schema the keymap can no longer be used to convert the keys
into a line number for an error message. NestedText provides the
normalize_key argument to load()
and loads()
to address this
issue. It allows you to pass in a function that normalizes the keys before the
keymap is created, releasing the schema from that task.
The following contact look-up program demonstrates both the normalization of keys and the associated error reporting. In this case, the first level of keys contains the names of the contacts and should not be normalized. Keys at all other levels are considered keywords and so should be normalized.
#!/usr/bin/env python3
"""
Display Contact Information
Usage:
contact <name>
"""
from docopt import docopt
from inform import codicil, display, error, full_stop, indent, os_error, terminate
import nestedtext as nt
from voluptuous import Schema, Required, Any, MultipleInvalid
import re
contacts_file = "address.nt"
def normalize_key(key, parent_keys):
if len(parent_keys) == 0:
return key
return ' '.join(key.lower().split())
def render_contact(data):
text = nt.dumps(data, default=repr)
return (re.sub(r'^(\s*)[>:]\s?(.*)$', r'\1\2', text, flags=re.M))
cmdline = docopt(__doc__)
name = cmdline['<name>']
try:
# define structure of contacts database
contacts_schema = Schema({
str: {
'position': str,
'address': str,
'phone': Required(Any({str:str},str)),
'email': Required(Any({str:str},str)),
'additional roles': Any(list,str),
}
})
# read contacts database
contacts = contacts_schema(
nt.load(
contacts_file,
top = 'dict',
normalize_key = normalize_key,
keymap = (keymap:={})
)
)
# display requested contact
for fullname, contact_info in contacts.items():
if name in fullname.lower():
display(fullname)
display(indent(render_contact(contact_info)))
except nt.NestedTextError as e:
e.report()
except MultipleInvalid as e:
for err in e.errors:
kind = 'key' if 'key' in err.msg else 'value'
keys = tuple(err.path)
codicil = keymap[keys].as_line(kind) if keys in keymap else None
error(
full_stop(err.msg),
culprit = (contacts_file, nt.join_keys(keys, keymap=keymap)),
codicil = codicil
)
except OSError as e:
error(os_error(e))
terminate()
This program takes a name as a command line argument and prints out the corresponding address. It uses the pretty print idea from the previous section to render the contact information. Voluptuous checks the validity of the contacts database, which is shown next. Notice the variability in the keys given in Fumiko’s entry:
# Contact information for our officers
Katheryn McDaniel:
position: president
address:
> 138 Almond Street
> Topeka, Kansas 20697
phone:
cell: 1-210-555-5297
home: 1-210-555-8470
email: KateMcD@aol.com
additional roles:
- board member
Margaret Hodge:
position: vice president
address:
> 2586 Marigold Lane
> Topeka, Kansas 20682
phone: 1-470-555-0398
email: margaret.hodge@ku.edu
additional roles:
- new membership task force
- accounting task force
Fumiko Purvis:
Position: treasurer
# Fumiko's term is ending at the end of the year.
# She will be replaced by Merrill Eldridge.
Address:
> 3636 Buffalo Ave
> Topeka, Kansas 20692
Phone: 1-268-555-0280
EMail: fumiko.purvis@hotmail.com
Additional Roles:
- accounting task force
Now, requesting Fumiko’s contact information gives:
Fumiko Purvis
position: treasurer
address:
3636 Buffalo Ave
Topeka, Kansas 20692
phone: 1-268-555-0280
email: fumiko.purvis@hotmail.com
additional roles:
- accounting task force
Notice that other than Fumiko’s name, the displayed keys are all normalized.
References¶
This example illustrates how one can implement references or macros in
NestedText. A reference allows you to define some content once and insert
that content multiple places in the document. This example also demonstrates
a slightly different way to implement validation and conversion on a per field
basis with voluptuous. Finally, it includes key normalization, which allows
the keys to be case insensitive and contain white space even though the program
that uses the data prefers the keys to be lower case identifiers. The
normalize_key function passed to load()
is used to transform the keys to
the desired form.
PostMortem is a program that generates a packet of information that is securely shared with your dependents in case of your death. Only the settings processing part of the package is shown here. Here is a configuration file that Odin might use to generate packets for his wife and kids:
my GPG ids: odin@norse-gods.com
sign with: @ my gpg ids
name template: {name}-{now:YYMMDD}
estate docs:
- ~/home/estate/trust.pdf
- ~/home/estate/will.pdf
- ~/home/estate/deed-valhalla.pdf
recipients:
Frigg:
email: frigg@norse-gods.com
category: wife
attach: @ estate docs
networth: odin
Thor:
email: thor@norse-gods.com
category: kids
attach: @ estate docs
Loki:
email: loki@norse-gods.com
category: kids
attach: @ estate docs
Notice that estate docs is defined at the top level. It is not a PostMortem
setting; it simply defines a value that will be interpolated into a setting
later. The interpolation is done by specifying @
along with the name of the
reference as a value. So for example, in recipients attach is specified as
@ estate docs
. This causes the list of estate documents to be used as
attachments. The same thing is done in sign with, which interpolates my gpg
ids.
Here is the code for validating and transforming the PostMortem settings:
#!/usr/bin/env python3
import nestedtext as nt
from pathlib import Path
from voluptuous import (
Schema, Invalid, MultipleInvalid, Extra, Required, REMOVE_EXTRA
)
from pprint import pprint
# Settings schema
# First define some functions that are used for validation and coercion
def to_str(arg):
if isinstance(arg, str):
return arg
raise Invalid('expected text')
def to_ident(arg):
arg = to_str(arg)
if arg.isidentifier():
return arg
raise Invalid('expected simple identifier')
def to_list(arg):
if isinstance(arg, str):
return arg.split()
if isinstance(arg, dict):
raise Invalid('expected list')
return arg
def to_paths(arg):
return [Path(p).expanduser() for p in to_list(arg)]
def to_email(arg):
user, _, host = arg.partition('@')
if '.' in host and '@' not in host:
return arg
raise Invalid('expected email address')
def to_emails(arg):
return [to_email(e) for e in to_list(arg)]
def to_gpg_id(arg):
try:
return to_email(arg) # gpg ID may be an email address
except Invalid:
try:
int(arg, base=16) # if not an email, it must be a hex key
assert len(arg) >= 8 # at least 8 characters long
return arg
except (ValueError, AssertionError):
raise Invalid('expected GPG id')
def to_gpg_ids(arg):
return [to_gpg_id(i) for i in to_list(arg)]
def to_snake_case(key):
return '_'.join(key.strip().lower().split())
# define the schema for the settings file
schema = Schema(
{
Required('my_gpg_ids'): to_gpg_ids,
'sign with': to_gpg_id,
'avendesora_gpg_passphrase_account': to_str,
'avendesora_gpg_passphrase_field': to_str,
'name template': to_str,
Required('recipients'): {
Extra: {
Required('category'): to_ident,
Required('email'): to_emails,
'gpg_id': to_gpg_id,
'attach': to_paths,
'networth': to_ident,
}
},
},
extra = REMOVE_EXTRA
)
# this function implements references
def expand_settings(value):
# allows macro values to be defined as a top-level setting.
# allows macro reference to be found anywhere.
if isinstance(value, str):
value = value.strip()
if value[:1] == '@':
value = settings[to_snake_case(value[1:])]
return value
if isinstance(value, dict):
return {k:expand_settings(v) for k, v in value.items()}
if isinstance(value, list):
return [expand_settings(v) for v in value]
raise NotImplementedError(value)
def normalize_key(key, parent_keys):
if parent_keys != ('recipients',):
# normalize all keys except the recipient names
return to_snake_case(key)
return key
try:
# Read settings
config_filepath = Path('postmortem.nt')
if config_filepath.exists():
# load from file
settings = nt.load(
config_filepath,
keymap = (keymap:={}),
normalize_key = normalize_key
)
# expand references
settings = expand_settings(settings)
# check settings and transform to desired types
settings = schema(settings)
# show the resulting settings
pprint(settings)
except nt.NestedTextError as e:
e.report()
except MultipleInvalid as e:
for err in e.errors:
kind = 'key' if 'key' in err.msg else 'value'
culprit = nt.join_keys(err.path, keymap=keymap)
print(f"ERROR: {config_filepath!s}: {culprit}: {err.msg}.")
try:
print(keymap[tuple(err.path)].as_line(kind))
except KeyError:
pass
except OSError as e:
print(f"ERROR: {config_filepath!s}: {e!s}")
This code uses expand_settings to implement references, and it uses the
Voluptuous schema to clean and validate the settings and convert them to
convenient forms. For example, the user could specify attach as a string or
a list, and the members could use a leading ~
to signify a home directory.
Applying to_paths in the schema converts whatever is specified to a list and
converts each member to a pathlib path with the ~
properly expanded.
Notice that the schema is defined in a different manner that the above examples. In those, you simply state which type you are expecting for the value and you use the Coerce function to indicate that the value should be cast to that type if needed. In this example, simple functions are passed in that perform validation and coercion as needed. This is a more flexible approach and allows better control of the error messages.
Here are the processed settings:
{'my_gpg_ids': ['odin@norse-gods.com'],
'recipients': {'Frigg': {'attach': [PosixPath('/home/ken/home/estate/trust.pdf'),
PosixPath('/home/ken/home/estate/will.pdf'),
PosixPath('/home/ken/home/estate/deed-valhalla.pdf')],
'category': 'wife',
'email': ['frigg@norse-gods.com'],
'networth': 'odin'},
'Loki': {'attach': [PosixPath('/home/ken/home/estate/trust.pdf'),
PosixPath('/home/ken/home/estate/will.pdf'),
PosixPath('/home/ken/home/estate/deed-valhalla.pdf')],
'category': 'kids',
'email': ['loki@norse-gods.com']},
'Thor': {'attach': [PosixPath('/home/ken/home/estate/trust.pdf'),
PosixPath('/home/ken/home/estate/will.pdf'),
PosixPath('/home/ken/home/estate/deed-valhalla.pdf')],
'category': 'kids',
'email': ['thor@norse-gods.com']}}}