I'm looking for a more pythonic way to update a field within a NamedTuple (from typing).
I get field name and value during runtime from a textfile und therefore used exec, but I believe, there must be a better way:
#!/usr/bin/env python3.6
# -*- coding: utf-8 -*-
from typing import NamedTuple
class Template (NamedTuple):
number : int = 0
name : str = "^NAME^"
oneInstance = Template()
print(oneInstance)
# If I know the variable name during development, I can do this:
oneInstance = oneInstance._replace(number = 77)
# I get this from a file during runtime:
para = {'name' : 'Jones'}
mykey = 'name'
# Therefore, I used exec:
ExpToEval = "oneInstance = oneInstance._replace(" + mykey + " = para[mykey])"
exec(ExpToEval) # How can I do this in a more pythonic (and secure) way?
print(oneInstance)
I guess, from 3.7 on, I could solve this issue with dataclasses, but I need it for 3.6
Using _replace on namedtuples can not be made "pythonic" whatsoever. Namedtuples are meant to be immutable. If you use a namedtuple other developers will expect that you do not intent to alter your data.
A pythonic approach is indeed the dataclass. You can use dataclasses in Python3.6 as well. Just use the dataclasses backport from PyPi.
Then the whole thing gets really readable and you can use getattrand setattr to address properties by name easily:
from dataclasses import dataclass
#dataclass
class Template:
number: int = 0
name: str = "^Name^"
t = Template()
# use setattr and getattr to access a property by a runtime-defined name
setattr(t, "name", "foo")
print(getattr(t, "name"))
This will result in
foo
Related
I'm trying to migrate a codebase from PyQt5 to PyQt6. I read in this article (see https://www.pythonguis.com/faq/pyqt5-vs-pyqt6/) that all enum members must be named using their fully qualified names. The article gives this example:
# PyQt5
widget = QCheckBox("This is a checkbox")
widget.setCheckState(Qt.Checked)
# PyQt6
widget = QCheckBox("This is a checkbox")
widget.setCheckState(Qt.CheckState.Checked)
Then the article continues:
"There are too many updated values to mention them all here. But if you're converting a codebase you can usually just search online for the short-form and the longer form will be in the results."
I get the point. This quote basically says something along the lines:
"If the Python interpreter runs into an error, and the error turns out to be a short-form enum, you'll likely find the solution online."
I get that. But this is not how I want to migrate the codebase. I want a full list of all the short-form enums and then perform a global search-and-replace for each.
Where can I find such a list?
I wrote a script to extract all the short-form and corresponding fully qualified enum names from the PyQt6 installation. It then does the conversions automatically:
# -*- coding: utf-8 -*-
# ================================================================================================ #
# ENUM CONVERTER TOOL #
# ================================================================================================ #
from typing import *
import os, argparse, inspect, re
q = "'"
help_text = '''
Copyright (c) 2022 Kristof Mulier
MIT licensed, see bottom
ENUM CONVERTER TOOL
===================
The script starts from the toplevel directory (assuming that you put this file in that directory)
and crawls through all the files and folders. In each file, it searches for old-style enums to
convert them into fully qualified names.
HOW TO USE
==========
Fill in the path to your PyQt6 installation folder. See line 57:
pyqt6_folderpath = 'C:/Python39/Lib/site-packages/PyQt6'
Place this script in the toplevel directory of your project. Open a terminal, navigate to the
directory and invoke this script:
$ python enum_converter_tool.py
WARNING
=======
This script modifies the files in your project! Make sure to backup your project before you put this
file inside. Also, you might first want to do a dry run:
$ python enum_converter_tool.py --dry_run
FEATURES
========
You can invoke this script in the following ways:
$ python enum_converter_tool.py No parameters. The script simply goes through
all the files and makes the replacements.
$ python enum_converter_tool.py --dry_run Dry run mode. The script won't do any replace-
ments, but prints out what it could replace.
$ python enum_converter_tool.py --show Print the dictionary this script creates to
convert the old-style enums into new-style.
$ python enum_converter_tool.py --help Show this help info
'''
# IMPORTANT: Point at the folder where PyQt6 stub files are located. This folder will be examined to
# fill the 'enum_dict'.
pyqt6_folderpath = 'C:/Python39/Lib/site-packages/PyQt6'
# Figure out where the toplevel directory is located. We assume that this converter tool is located
# in that directory. An os.walk() operation starts from this toplevel directory to find and process
# all files.
toplevel_directory = os.path.realpath(
os.path.dirname(
os.path.realpath(
inspect.getfile(
inspect.currentframe()
)
)
)
).replace('\\', '/')
# Figure out the name of this script. It will be used later on to exclude oneself from the replace-
# ments.
script_name = os.path.realpath(
inspect.getfile(inspect.currentframe())
).replace('\\', '/').split('/')[-1]
# Create the dictionary that will be filled with enums
enum_dict:Dict[str, str] = {}
def fill_enum_dict(filepath:str) -> None:
'''
Parse the given stub file to extract the enums and flags. Each one is inside a class, possibly a
nested one. For example:
---------------------------------------------------------------------
| class Qt(PyQt6.sip.simplewrapper): |
| class HighDpiScaleFactorRoundingPolicy(enum.Enum): |
| Round = ... # type: Qt.HighDpiScaleFactorRoundingPolicy |
---------------------------------------------------------------------
The enum 'Round' is from class 'HighDpiScaleFactorRoundingPolicy' which is in turn from class
'Qt'. The old reference style would then be:
> Qt.Round
The new style (fully qualified name) would be:
> Qt.HighDpiScaleFactorRoundingPolicy.Round
The aim of this function is to fill the 'enum_dict' with an entry like:
enum_dict = {
'Qt.Round' : 'Qt.HighDpiScaleFactorRoundingPolicy.Round'
}
'''
content:str = ''
with open(filepath, 'r', encoding='utf-8', newline='\n', errors='replace') as f:
content = f.read()
p = re.compile(r'(\w+)\s+=\s+\.\.\.\s+#\s*type:\s*([\w.]+)')
for m in p.finditer(content):
# Observe the enum's name, eg. 'Round'
enum_name = m.group(1)
# Figure out in which classes it is
class_list = m.group(2).split('.')
# If it belongs to just one class (no nesting), there is no point in continuing
if len(class_list) == 1:
continue
# Extract the old and new enum's name
old_enum = f'{class_list[0]}.{enum_name}'
new_enum = ''
for class_name in class_list:
new_enum += f'{class_name}.'
continue
new_enum += enum_name
# Add them to the 'enum_dict'
enum_dict[old_enum] = new_enum
continue
return
def show_help() -> None:
'''
Print help info and quit.
'''
print(help_text)
return
def convert_enums_in_file(filepath:str, dry_run:bool) -> None:
'''
Convert the enums in the given file.
'''
filename:str = filepath.split('/')[-1]
# Ignore the file in some cases
if any(filename == fname for fname in (script_name, )):
return
# Read the content
content:str = ''
with open(filepath, 'r', encoding='utf-8', newline='\n', errors='replace') as f:
content = f.read()
# Loop over all the keys in the 'enum_dict'. Perform a replacement in the 'content' for each of
# them.
for k, v in enum_dict.items():
if k not in content:
continue
# Compile a regex pattern that only looks for the old enum (represented by the key of the
# 'enum_dict') if it is surrounded by bounds. What we want to avoid is a situation like
# this:
# k = 'Qt.Window'
# k found in 'qt.Qt.WindowType.Window'
# In the situation above, k is found in 'qt.Qt.WindowType.Window' such that a replacement
# will take place there, messing up the code! By surrounding k with bounds in the regex pat-
# tern, this won't happen.
p = re.compile(fr'\b{k}\b')
# Substitute all occurences of k (key) in 'content' with v (value). The 'subn()' method re-
# turns a tuple (new_string, number_of_subs_made).
new_content, n = p.subn(v, content)
if n == 0:
assert new_content == content
continue
assert new_content != content
print(f'{q}{filename}{q}: Replace {q}{k}{q} => {q}{v}{q} ({n})')
content = new_content
continue
if dry_run:
return
with open(filepath, 'w', encoding='utf-8', newline='\n', errors='replace') as f:
f.write(content)
return
def convert_all(dry_run:bool) -> None:
'''
Search and replace all enums.
'''
for root, dirs, files in os.walk(toplevel_directory):
for f in files:
if not f.endswith('.py'):
continue
filepath = os.path.join(root, f).replace('\\', '/')
convert_enums_in_file(filepath, dry_run)
continue
continue
return
if __name__ == '__main__':
parser = argparse.ArgumentParser(
description = 'Convert enums to fully-qualified names',
add_help = False,
)
parser.add_argument('-h', '--help' , action='store_true')
parser.add_argument('-d', '--dry_run' , action='store_true')
parser.add_argument('-s', '--show' , action='store_true')
args = parser.parse_args()
if args.help:
show_help()
else:
#& Check if 'pyqt6_folderpath' exists
if not os.path.exists(pyqt6_folderpath):
print(
f'\nERROR:\n'
f'Folder {q}{pyqt6_folderpath}{q} could not be found. Make sure that variable '
f'{q}pyqt6_folderpath{q} from line 57 points to the PyQt6 installation folder.\n'
)
else:
#& Fill the 'enum_dict'
type_hint_files = [
os.path.join(pyqt6_folderpath, _filename)
for _filename in os.listdir(pyqt6_folderpath)
if _filename.endswith('.pyi')
]
for _filepath in type_hint_files:
fill_enum_dict(_filepath)
continue
#& Perform requested action
if args.show:
import pprint
pprint.pprint(enum_dict)
elif args.dry_run:
print('\nDRY RUN\n')
convert_all(dry_run=True)
else:
convert_all(dry_run=False)
print('\nQuit enum converter tool\n')
# MIT LICENSE
# ===========
# Copyright (c) 2022 Kristof Mulier
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this software and
# associated documentation files (the "Software"), to deal in the Software without restriction, in-
# cluding without limitation the rights to use, copy, modify, merge, publish, distribute, sublicen-
# se, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to
# do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all copies or substan-
# tial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT
# NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRIN-
# GEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
# OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
# CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
Make sure you backup your Python project. Then place this file in the toplevel directory of the project. Modify line 57 (!) such that it points to your PyQt6 installation folder.
First run the script with the --dry_run flag to make sure you agree with the replacements. Then run it without any flags.
I'm running Python 3.8.10 and have a dataclass with some attributes. Some of them have a default value but are not part of the constructor.
Attributes which have the init value set to False are not showing up in the object dict.
Is this the expected behavior? How can I force these attributes to show up in vars?
from dataclasses import dataclass, field
#dataclass
class Book:
name: str = field(default="", init=False)
author: str = field(default="", init=True)
b = Book()
b
> Book(name='', author='')
b.name
> ''
b.author
> ''
## name does not show up here
vars(b)
> {'author': ''}
b.__dict__
> {'author': ''}
I just hit the same issue. Some experimenting showed me that these variables show up in vars after they have been set.
I added the following to my __post_init__() and then they showed up in vars
def __post_init__(self):
for field in dataclasses.fields(self):
#Ensure that all dataclass fields show up in vars
if field.name not in vars(self):
setattr(self, field.name, getattr(self, field.name))
The docs also mention some other weirdness with using init=False. https://docs.python.org/3/library/dataclasses.html#dataclasses.replace
Be forewarned about how init=False fields work during a call to
replace(). They are not copied from the source object, but rather are
initialized in post_init(), if they’re initialized at all. It is
expected that init=False fields will be rarely and judiciously used.
Definitely check your assumptions when it comes to this feature I think.
I would like SQLAlchemy to return an error if the underlying SQLite3 database file does not exist.
I've looked around, and tried:
#!/usr/bin/env python3
from sqlalchemy import create_engine, Column, Integer
from sqlalchemy.orm import Session, declarative_base
Base = declarative_base()
class SomeTable(Base):
id = Column(Integer)
DB_SPECIFIER = 'sqlite+pysqlite:////tmp/non-exist.db?mode=rw'
engine = create_engine(DB_SPECIFIER, echo=False, future=True, connect_args={'uri': True})
session = Session(engine)
x = session.query(SomeTable)
I'd like the create_engine call to fail if /tmp/non-exist.db does not exist. I thought using this answer would work, but it did not.
Looks like it's in the docs, though fairly hidden:
https://docs.sqlalchemy.org/en/14/dialects/sqlite.html#uri-connections
So you'd do:
DB_SPECIFIER = 'sqlite:///file:/tmp/non-exist.db?mode=ro&uri=true'
engine = create_engine(DB_SPECIFIER, echo=False, future=True)
It picks this apart and sends arguments to the connection, the rest through to the URI. (You can also add some lock disabling and such there, if that helps, since it's read only).
I am doing a project in Python, django rest framework. I am using haystack SearchQuerySet. My code is here.
from haystack import indexes
from Medications.models import Salt
class Salt_Index(indexes.SearchIndex, indexes.Indexable):
text = indexes.CharField(document=True, use_template=True)
name = indexes.CharField(model_attr='name',null=True)
slug = indexes.CharField(model_attr='slug',null=True)
if_i_forget = indexes.CharField(model_attr='if_i_forget',null=True)
other_information = indexes.CharField(model_attr='other_information',null=True)
precautions = indexes.CharField(model_attr='precautions',null=True)
special_dietary = indexes.CharField(model_attr='special_dietary',null=True)
brand = indexes.CharField(model_attr='brand',null=True)
why = indexes.CharField(model_attr='why',null=True)
storage_conditions = indexes.CharField(model_attr='storage_conditions',null=True)
side_effects = indexes.CharField(model_attr='side_effects',null=True)
def get_model(self):
return Salt
def index_queryset(self, using=None):
return self.get_model().objects.all()
and my views.py file is -
from django.views.generic import View
from haystack.query import SearchQuerySet
from django.core import serializers
class Medication_Search_View(View):
def get(self,request,format=None):
try:
get_data = SearchQuerySet().all()
print get_data
serialized = ss.serialize("json", [data.object for data in get_data])
return HttpResponse(serialized)
except Exception,e:
print e
my python manage.py rebuild_index is working fine (showing 'Indexing 2959 salts') but in my 'views.py' file , SearchQuerySet() is returning an empty query set...
I am very much worried for this. Please help me friends if you know the reason behind getting empty query set while I have data in my Salt model.
you should check app name it is case sensitive.try to write app name in small letters
My problem is solved now. The problem was that i had wriiten apps name with capital letters and the database tables were made in small letters(myapp_Student). so it was creating problem on database lookup.
I am new to Pig and I want to convert a bag of tuples to a map with specific value in each tuple as key. Basically I want to change:
{(id1, value1),(id2, value2), ...} into [id1#value1, id2#value2]
I've been looking around online for a while, but I can't seem to find a solution. I've tried:
bigQMap = FOREACH bigQFields GENERATE TOMAP(queryId, queryStart);
but I end up with a bag of maps (e.g. {[id1#value1], [id2#value2], ...}), which is not what I want. How can I build up a map out of a bag of key-value tuple?
Below is the specific script I'm trying to run, in case it's relevant
rawlines = LOAD '...' USING PigStorage('`');
bigQFields = FOREACH bigQLogs GENERATE GFV(*,'queryId')
as queryId, GFV(*, 'queryStart')
as queryStart;
bigQMap = ?? how to make a map with queryId as key and queryStart as value ?? ;
TOMAP takes a series of pairs and converts them into the map, so it is meant to be used like:
-- Schema: A:{foo:chararray, bar:int, bing:chararray, bang:int}
-- Data: (John, 27, Joe, 30)
B = FOREACH A GENERATE TOMAP(foo, bar, bing, bang) AS m ;
-- Schema: B:{m: map[]}
-- Data: (John#27,Joe#30)
So as you can see the syntax does not support converting a bag to a map. As far as I know there is no way to convert a bag in the format you have to map in pure pig. However, you can definitively write a java UDF to do this.
NOTE: I'm not too experienced with java, so this UDF can easily be improved on (adding exception handling, what happens if a key added twice etc.). However, it does accomplish what you need it to.
package myudfs;
import java.io.IOException;
import org.apache.pig.EvalFunc;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import org.apache.pig.data.Tuple;
import org.apache.pig.data.DataBag;
public class ConvertToMap extends EvalFunc<Map>
{
public Map exec(Tuple input) throws IOException {
DataBag values = (DataBag)input.get(0);
Map<Object, Object> m = new HashMap<Object, Object>();
for (Iterator<Tuple> it = values.iterator(); it.hasNext();) {
Tuple t = it.next();
m.put(t.get(0), t.get(1));
}
return m;
}
}
Once you compile the script into a jar, it can be used like:
REGISTER myudfs.jar ;
-- A is loading some sample data I made
A = LOAD 'foo.in' AS (foo:{T:(id:chararray, value:chararray)}) ;
B = FOREACH A GENERATE myudfs.ConvertToMap(foo) AS bar;
Contents of foo.in:
{(open,apache),(apache,hadoop)}
{(foo,bar),(bar,foo),(open,what)}
Output from B:
([open#apache,apache#hadoop])
([bar#foo,open#what,foo#bar])
Another approach is to use python to create the UDF:
myudfs.py
#!/usr/bin/python
#outputSchema("foo:map[]")
def BagtoMap(bag):
d = {}
for key, value in bag:
d[key] = value
return d
Which is used like this:
Register 'myudfs.py' using jython as myfuncs;
-- A is still just loading some of my test data
A = LOAD 'foo.in' AS (foo:{T:(key:chararray, value:chararray)}) ;
B = FOREACH A GENERATE myfuncs.BagtoMap(foo) ;
And produces the same output as the Java UDF.
BONUS:
Since I don't like maps very much, here is a link explaining how the functionality of a map can be replicated with just key value pairs. Since your key value pairs are in a bag, you'll need to do the map-like operations in a nested FOREACH:
-- A is a schema that contains kv_pairs, a bag in the form {(id, value)}
B = FOREACH A {
temp = FOREACH kv_pairs GENERATE (key=='foo'?value:NULL) ;
-- Output is like: ({(),(thevalue),(),()})
-- MAX will pull the maximum value from the filtered bag, which is
-- value (the chararray) if the key matched. Otherwise it will return NULL.
GENERATE MAX(temp) as kv_pairs_filtered ;
}
I ran into the same situation so I submitted a patch that just got accepted: https://issues.apache.org/jira/browse/PIG-4638
This means that what you wanted is a core part starting with pig 0.16.