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+--- Thread: meaning of -> syntax in function definition (/thread-36884.html)
meaning of -> syntax in function definition - DrakeSoft - Apr-08-2022
Hi,
I came across the following function:
def getWords(self) -> list[str]:
with open(self.word_list_path, "r") as f:
word_list = [line.strip() for line in f]
return word_list
class Ui_MainWindow(QMainWindow):
def __init__(self, word_list_path: str):
super().__init__()
self.word_list_path = word_list_path
self.speller = SpellCheckWrapper(self.getWords(), self.addToDictionary)
self.setupUi()
class SpellCheckWrapper:
def __init__(
self, personal_word_list: list[str], addToDictionary: Callable[[str], None]
):
# Creating temporary file
self.file = QTemporaryFile()
self.file.open()
self.dictionary = DictWithPWL(
"en_US",
.......I am not familiar with the notation "def getWords(self) -> list[str]:" in the function definition. What does the -> mean?Also when I invoke the file with python3 I get an error on the line:
self.speller = SpellCheckWrapper(self.getWords(), self.addToDictionary)TypeError: 'type' object is not subscriptable
Could someone explain or provide some context for the use of -> and the error I see?
RE: meaning of -> syntax in function definition - deanhystad - Apr-08-2022
The "->" is part of the relatively new (version 3.5) Python type annotations. Think of type annotations as a way to document variable and function return types. An annotation standard allows development of code checking tools and documentation tools. Annotations do not change how Python runs the code. I would change "->list[str]" to "->List[str]", but this is not going to cause an errors.
Everything you 'd ever want to know about type annotations:
https://docs.python.org/3/library/typing.html
https://peps.python.org/pep-0484/
https://peps.python.org/pep-0483/
The annotations are not causing your error. I cannot help you because that is the only thing I know about your error. When you have an error please post the entire error message including the traceback. I would also like to see more complete code. This instruction is not correct for the code you have posed:
self.speller = SpellCheckWrapper(self.getWords(), self.addToDictionary)According to this line, getWords() is a method of Ui_MainWindow, but it does not look like that in your posted code.
RE: meaning of -> syntax in function definition - Yoriz - Apr-08-2022
If you are using a version older than 3.9 you would need to import
List from the typing modulefrom typing import List
def getWords(self) -> List[str]:
....From version python 3.9 you can use the built-in
list as a type hint.def getWords(self) -> list[str]:
....https://docs.python.org/3.9/whatsnew/3.9.html#type-hinting-generics-in-standard-collections Wrote:Type Hinting Generics in Standard Collections
In type annotations you can now use built-in collection types such as list and dict as generic types instead of importing the corresponding capitalized types (e.g. List or Dict) from typing. Some other types in the standard library are also now generic, for example queue.Queue.
Example:
def greet_all(names: list[str]) -> None: for name in names: print("Hello", name)See PEP 585 for more details. (Contributed by Guido van Rossum, Ethan Smith, and Batuhan Taşkaya in bpo-39481.)
RE: meaning of -> syntax in function definition - DrakeSoft - Apr-08-2022
Thank you for your reply
I have included the complete code:
#example.py
import sys
from PyQt5.QtWidgets import QApplication, QMainWindow, QVBoxLayout, QWidget
from spellcheckwrapper import SpellCheckWrapper
from spelltextedit import SpellTextEdit
class Ui_MainWindow(QMainWindow):
def __init__(self, word_list_path: str):
super().__init__()
self.word_list_path = word_list_path
self.speller = SpellCheckWrapper(self.getWords(), self.addToDictionary)
self.setupUi()
def setupUi(self):
self.resize(500, 500)
self.setWindowTitle("Example app")
self.centralWidget = QWidget(self)
self.setCentralWidget(self.centralWidget)
self.layout = QVBoxLayout(self.centralWidget)
self.centralWidget.setLayout(self.layout)
self.textEdit1 = SpellTextEdit(self.speller, self.centralWidget)
self.layout.addWidget(self.textEdit1)
self.textEdit2 = SpellTextEdit(self.speller, self.centralWidget)
self.layout.addWidget(self.textEdit2)
def getWords(self) -> list[str]:
with open(self.word_list_path, "r") as f:
word_list = [line.strip() for line in f]
return word_list
def addToDictionary(self, new_word: str):
with open(self.word_list_path, "a") as f:
f.write("\n" + new_word)
if __name__ == "__main__":
app = QApplication(sys.argv)
window = Ui_MainWindow("example_word_list.txt")
window.show()
sys.exit(app.exec_())
#------------------------
#spellcheckhighlighter.py
import re
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QSyntaxHighlighter, QTextCharFormat
from spellcheckwrapper import SpellCheckWrapper
class SpellCheckHighlighter(QSyntaxHighlighter):
wordRegEx = re.compile(r"\b([A-Za-z]{2,})\b")
def highlightBlock(self, text: str) -> None:
if not hasattr(self, "speller"):
return
self.misspelledFormat = QTextCharFormat()
self.misspelledFormat.setUnderlineStyle(QTextCharFormat.SpellCheckUnderline)
self.misspelledFormat.setUnderlineColor(Qt.red)
for word_object in self.wordRegEx.finditer(text):
if not self.speller.check(word_object.group()):
self.setFormat(
word_object.start(),
word_object.end() - word_object.start(),
self.misspelledFormat,
)
def setSpeller(self, speller: SpellCheckWrapper):
self.speller = speller
#------------------------------------
from typing import Callable
import enchant
from enchant import DictWithPWL
from PyQt5.QtCore import QTemporaryFile
class SpellCheckWrapper:
def __init__(
self, personal_word_list: list[str], addToDictionary: Callable[[str], None]
):
# Creating temporary file
self.file = QTemporaryFile()
self.file.open()
self.dictionary = DictWithPWL(
"en_US",
self.file.fileName(),
)
self.addToDictionary = addToDictionary
self.word_list = set(personal_word_list)
self.load_words()
def load_words(self):
for word in self.word_list:
self.dictionary.add(word)
def suggestions(self, word: str) -> list[str]:
return self.dictionary.suggest(word)
def correction(self, word: str) -> str:
return self.dictionary.suggest(word)[0]
def add(self, new_word: str) -> bool:
if self.check(new_word):
return False
self.word_list.add(new_word)
self.addToDictionary(new_word)
self.dictionary.add(new_word)
return True
def check(self, word: str) -> bool:
return self.dictionary.check(word)
def getNewWords(self) -> set[str]:
return self.word_list
#--------------------------------------------
# highlighter.py
import re
from PyQt5.QtCore import Qt
from PyQt5.QtGui import QSyntaxHighlighter, QTextCharFormat
from spellcheckwrapper import SpellCheckWrapper
class SpellCheckHighlighter(QSyntaxHighlighter):
wordRegEx = re.compile(r"\b([A-Za-z]{2,})\b")
def highlightBlock(self, text: str) -> None:
if not hasattr(self, "speller"):
return
self.misspelledFormat = QTextCharFormat()
self.misspelledFormat.setUnderlineStyle(QTextCharFormat.SpellCheckUnderline)
self.misspelledFormat.setUnderlineColor(Qt.red)
for word_object in self.wordRegEx.finditer(text):
if not self.speller.check(word_object.group()):
self.setFormat(
word_object.start(),
word_object.end() - word_object.start(),
self.misspelledFormat,
)
def setSpeller(self, speller: SpellCheckWrapper):
self.speller = speller
#
# correction_action.py
from PyQt5.QtCore import pyqtSignal
from PyQt5.QtWidgets import QAction
class SpecialAction(QAction):
actionTriggered = pyqtSignal(str)
def __init__(self, *args):
super().__init__(*args)
self.triggered.connect(self.emitTriggered)
def emitTriggered(self):
self.actionTriggered.emit(self.text())The error message isError:Traceback (most recent call last):
File "/home/ProtoTyping/SpellChecker/pyqt-spellcheck/src/example.py", line 5, in <module>
from spellcheckwrapper import SpellCheckWrapper
File "/home/ProtoTyping/SpellChecker/pyqt-spellcheck/src/spellcheckwrapper.py", line 7, in <module>
class SpellCheckWrapper:
File "/home/ProtoTyping/SpellChecker/pyqt-spellcheck/src/spellcheckwrapper.py", line 9, in SpellCheckWrapper
self, personal_word_list: list[str], addToDictionary: Callable[[str], None]
TypeError: 'type' object is not subscriptableRE: meaning of -> syntax in function definition - deanhystad - Apr-08-2022
As Yoriz mentioned, if you are using Python 3.9 or newer you can use list[str]. If you are using an older version of Python you need to use List[str] and in spellecheckwrapper.py modify the import.
from typing import Callable, List
RE: meaning of -> syntax in function definition - DrakeSoft - Apr-09-2022
Thanks guys,
When I did a python --version it was showing me Python 3.9.7, so the original code should have worked. But I was running the code in VScode, so I guess it was using an earlier version.
In the settings of VSCode, I changed the interpreter from Python3 (which was defaulting to /usr/bin/python3 --version Python 3.8.10) to Python 3.9.7 and then the code ran fine in vscode also.
again, thank you for your help, very much appreciated!