宜配屋

python3+PyQt5泛型委托详解

yipeiwu_com6年前Python基础

自定义委托可以让我们对视图中出现的数据项的外观和行为进行完全控制。如果有很多模型，可能会希望不是全部的大多数模型能够仅用一个自定义委托，如果不能这么做，那么对于这些自定义委托，将很有可能存在大量重复代码。为了使得维护工作变得轻松，更好的方法为不要为每个模型创建一个自定义委托，而是用一系列的通用组件来共同构成一个委托。本文通过Python3+pyqt5实现了python Qt GUI 快速编程的16章的泛型委托例子。

/home/yrd/eric_workspace/chap16/richtextlineedit.py

#!/usr/bin/env python3

import platform
import sys
import html
from PyQt5.QtCore import QSize, Qt,pyqtSignal
from PyQt5.QtGui import QColor, QFont,QFontMetrics, QIcon, QKeySequence, QPixmap,QTextCharFormat
from PyQt5.QtWidgets import QAction,QApplication,QMenu,QTextEdit


class RichTextLineEdit(QTextEdit):
 returnPressed=pyqtSignal()
 (Bold, Italic, Underline, StrikeOut, Monospaced, Sans, Serif,
  NoSuperOrSubscript, Subscript, Superscript) = range(10)


 def __init__(self, parent=None):
  super(RichTextLineEdit, self).__init__(parent)

  self.monofamily = "courier"
  self.sansfamily = "helvetica"
  self.seriffamily = "times"
  self.setLineWrapMode(QTextEdit.NoWrap)
  self.setTabChangesFocus(True)
  self.setVerticalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
  self.setHorizontalScrollBarPolicy(Qt.ScrollBarAlwaysOff)
  fm = QFontMetrics(self.font())
  h = int(fm.height() * (1.4 if platform.system() == "Windows"
         else 1.2))
  self.setMinimumHeight(h)
  self.setMaximumHeight(int(h * 1.2))
  self.setToolTip("Press <b>Ctrl+M</b> for the text effects "
    "menu and <b>Ctrl+K</b> for the color menu")


 def toggleItalic(self):
  self.setFontItalic(not self.fontItalic())


 def toggleUnderline(self):
  self.setFontUnderline(not self.fontUnderline())


 def toggleBold(self):
  self.setFontWeight(QFont.Normal
    if self.fontWeight() > QFont.Normal else QFont.Bold)


 def sizeHint(self):
  return QSize(self.document().idealWidth() + 5,
      self.maximumHeight())


 def minimumSizeHint(self):
  fm = QFontMetrics(self.font())
  return QSize(fm.width("WWWW"), self.minimumHeight())


 def contextMenuEvent(self, event):
  self.textEffectMenu()


 def keyPressEvent(self, event):
  if event.modifiers() & Qt.ControlModifier:
   handled = False
   if event.key() == Qt.Key_B:
    self.toggleBold()
    handled = True
   elif event.key() == Qt.Key_I:
    self.toggleItalic()
    handled = True
   elif event.key() == Qt.Key_K:
    self.colorMenu()
    handled = True
   elif event.key() == Qt.Key_M:
    self.textEffectMenu()
    handled = True
   elif event.key() == Qt.Key_U:
    self.toggleUnderline()
    handled = True
   if handled:
    event.accept()
    return
  if event.key() in (Qt.Key_Enter, Qt.Key_Return):
   self.returnPressed.emit()
   event.accept()
  else:
   QTextEdit.keyPressEvent(self, event)


 def colorMenu(self):
  pixmap = QPixmap(22, 22)
  menu = QMenu("Colour")
  for text, color in (
    ("&Black", Qt.black),
    ("B&lue", Qt.blue),
    ("Dark Bl&ue", Qt.darkBlue),
    ("&Cyan", Qt.cyan),
    ("Dar&k Cyan", Qt.darkCyan),
    ("&Green", Qt.green),
    ("Dark Gr&een", Qt.darkGreen),
    ("M&agenta", Qt.magenta),
    ("Dark Mage&nta", Qt.darkMagenta),
    ("&Red", Qt.red),
    ("&Dark Red", Qt.darkRed)):
   color = QColor(color)
   pixmap.fill(color)
   action = menu.addAction(QIcon(pixmap), text, self.setColor)
   action.setData(color)
  self.ensureCursorVisible()
  menu.exec_(self.viewport().mapToGlobal(
     self.cursorRect().center()))


 def setColor(self):
  action = self.sender()
  if action is not None and isinstance(action, QAction):
   color = QColor(action.data())
   if color.isValid():
    self.setTextColor(color)


 def textEffectMenu(self):
  format = self.currentCharFormat()
  menu = QMenu("Text Effect")
  for text, shortcut, data, checked in (
    ("&Bold", "Ctrl+B", RichTextLineEdit.Bold,
     self.fontWeight() > QFont.Normal),
    ("&Italic", "Ctrl+I", RichTextLineEdit.Italic,
     self.fontItalic()),
    ("Strike &out", None, RichTextLineEdit.StrikeOut,
     format.fontStrikeOut()),
    ("&Underline", "Ctrl+U", RichTextLineEdit.Underline,
     self.fontUnderline()),
    ("&Monospaced", None, RichTextLineEdit.Monospaced,
     format.fontFamily() == self.monofamily),
    ("&Serifed", None, RichTextLineEdit.Serif,
     format.fontFamily() == self.seriffamily),
    ("S&ans Serif", None, RichTextLineEdit.Sans,
     format.fontFamily() == self.sansfamily),
    ("&No super or subscript", None,
     RichTextLineEdit.NoSuperOrSubscript,
     format.verticalAlignment() ==
     QTextCharFormat.AlignNormal),
    ("Su&perscript", None, RichTextLineEdit.Superscript,
     format.verticalAlignment() ==
     QTextCharFormat.AlignSuperScript),
    ("Subs&cript", None, RichTextLineEdit.Subscript,
     format.verticalAlignment() ==
     QTextCharFormat.AlignSubScript)):
   action = menu.addAction(text, self.setTextEffect)
   if shortcut is not None:
    action.setShortcut(QKeySequence(shortcut))
   action.setData(data)
   action.setCheckable(True)
   action.setChecked(checked)
  self.ensureCursorVisible()
  menu.exec_(self.viewport().mapToGlobal(
     self.cursorRect().center()))


 def setTextEffect(self):
  action = self.sender()
  if action is not None and isinstance(action, QAction):
   what = action.data()
   if what == RichTextLineEdit.Bold:
    self.toggleBold()
    return
   if what == RichTextLineEdit.Italic:
    self.toggleItalic()
    return
   if what == RichTextLineEdit.Underline:
    self.toggleUnderline()
    return
   format = self.currentCharFormat()
   if what == RichTextLineEdit.Monospaced:
    format.setFontFamily(self.monofamily)
   elif what == RichTextLineEdit.Serif:
    format.setFontFamily(self.seriffamily)
   elif what == RichTextLineEdit.Sans:
    format.setFontFamily(self.sansfamily)
   if what == RichTextLineEdit.StrikeOut:
    format.setFontStrikeOut(not format.fontStrikeOut())
   if what == RichTextLineEdit.NoSuperOrSubscript:
    format.setVerticalAlignment(
      QTextCharFormat.AlignNormal)
   elif what == RichTextLineEdit.Superscript:
    format.setVerticalAlignment(
      QTextCharFormat.AlignSuperScript)
   elif what == RichTextLineEdit.Subscript:
    format.setVerticalAlignment(
      QTextCharFormat.AlignSubScript)
   self.mergeCurrentCharFormat(format)


 def toSimpleHtml(self):
  htmltext = ""
  black = QColor(Qt.black)
  block = self.document().begin()
  while block.isValid():
   iterator = block.begin()
   while iterator != block.end():
    fragment = iterator.fragment()
    if fragment.isValid():
     format = fragment.charFormat()
     family = format.fontFamily()
     color = format.foreground().color()     
     text=html.escape(fragment.text())
     if (format.verticalAlignment() ==
      QTextCharFormat.AlignSubScript):
      text = "<sub>{0}</sub>".format(text)
     elif (format.verticalAlignment() ==
       QTextCharFormat.AlignSuperScript):
      text = "<sup>{0}</sup>".format(text)
     if format.fontUnderline():
      text = "<u>{0}</u>".format(text)
     if format.fontItalic():
      text = "<i>{0}</i>".format(text)
     if format.fontWeight() > QFont.Normal:
      text = "<b>{0}</b>".format(text)
     if format.fontStrikeOut():
      text = "<s>{0}</s>".format(text)
     if color != black or family:
      attribs = ""
      if color != black:
       attribs += ' color="{0}"'.format(color.name())
      if family:
       attribs += ' face="{0}"'.format(family)
      text = "<font{0}>{1}</font>".format(attribs,text)
     htmltext += text
    iterator += 1
   block = block.next()
  return htmltext

if __name__ == "__main__":
 def printout(lineedit):
  print(str(lineedit.toHtml()))
  print(str(lineedit.toPlainText()))
  print(str(lineedit.toSimpleHtml()))    
 app = QApplication(sys.argv)
 lineedit = RichTextLineEdit()
 lineedit.returnPressed.connect(lambda:printout(lineedit))
 lineedit.show()
 lineedit.setWindowTitle("RichTextEdit")
 app.exec_()

/home/yrd/eric_workspace/chap16/genericdelegates.py

#!/usr/bin/env python3

from PyQt5.QtCore import (QDate, QSize, Qt)
from PyQt5.QtWidgets import (QApplication, QDateEdit, QLineEdit,
  QSpinBox, QStyledItemDelegate,QStyle)
from PyQt5.QtGui import QColor,QTextDocument
import richtextlineedit


class GenericDelegate(QStyledItemDelegate):

 def __init__(self, parent=None):
  super(GenericDelegate, self).__init__(parent)
  self.delegates = {}


 def insertColumnDelegate(self, column, delegate):
  delegate.setParent(self)
  self.delegates[column] = delegate


 def removeColumnDelegate(self, column):
  if column in self.delegates:
   del self.delegates[column]


 def paint(self, painter, option, index):
  delegate = self.delegates.get(index.column())
  if delegate is not None:
   delegate.paint(painter, option, index)
  else:
   QStyledItemDelegate.paint(self, painter, option, index)


 def createEditor(self, parent, option, index):
  delegate = self.delegates.get(index.column())
  if delegate is not None:
   return delegate.createEditor(parent, option, index)
  else:
   return QStyledItemDelegate.createEditor(self, parent, option,
             index)


 def setEditorData(self, editor, index):
  delegate = self.delegates.get(index.column())
  if delegate is not None:
   delegate.setEditorData(editor, index)
  else:
   QStyledItemDelegate.setEditorData(self, editor, index)


 def setModelData(self, editor, model, index):
  delegate = self.delegates.get(index.column())
  if delegate is not None:
   delegate.setModelData(editor, model, index)
  else:
   QStyledItemDelegate.setModelData(self, editor, model, index)


class IntegerColumnDelegate(QStyledItemDelegate):

 def __init__(self, minimum=0, maximum=100, parent=None):
  super(IntegerColumnDelegate, self).__init__(parent)
  self.minimum = minimum
  self.maximum = maximum


 def createEditor(self, parent, option, index):
  spinbox = QSpinBox(parent)
  spinbox.setRange(self.minimum, self.maximum)
  spinbox.setAlignment(Qt.AlignRight|Qt.AlignVCenter)
  return spinbox


 def setEditorData(self, editor, index):
  value = index.model().data(index, Qt.DisplayRole)
  editor.setValue(value)


 def setModelData(self, editor, model, index):
  editor.interpretText()
  model.setData(index, editor.value())


class DateColumnDelegate(QStyledItemDelegate):

 def __init__(self, minimum=QDate(),
     maximum=QDate.currentDate(),
     format="yyyy-MM-dd", parent=None):
  super(DateColumnDelegate, self).__init__(parent)
  self.minimum = minimum
  self.maximum = maximum
  self.format = format


 def createEditor(self, parent, option, index):
  dateedit = QDateEdit(parent)
  #dateedit=QDateTimeEdit(parent)
  dateedit.setDateRange(self.minimum, self.maximum)
  dateedit.setAlignment(Qt.AlignRight|Qt.AlignVCenter)
  dateedit.setDisplayFormat(self.format)
  dateedit.setCalendarPopup(True)
  return dateedit


 def setEditorData(self, editor, index):
  value = index.model().data(index, Qt.DisplayRole)
  #if value.isNull:
  editor.setDate(value)
  #editor.setDisplayFormat(self.format)

 def setModelData(self, editor, model, index):
  model.setData(index, editor.date())
 def paint(self, painter, option, index):
  text = index.model().data(index, Qt.DisplayRole).toString(self.format)
  palette = QApplication.palette()
  document = QTextDocument()
  document.setDefaultFont(option.font)
  if option.state & QStyle.State_Selected:
   document.setHtml("<font color={0}>{1}</font>".format(palette.highlightedText().color().name(),text))
  else:
   document.setHtml(text)
  painter.save()
  color = (palette.highlight().color()
     if option.state & QStyle.State_Selected
     else QColor(index.model().data(index,
        Qt.BackgroundColorRole)))
  painter.fillRect(option.rect, color)
  painter.translate(option.rect.x(), option.rect.y())
  document.drawContents(painter)
  painter.restore()  


class PlainTextColumnDelegate(QStyledItemDelegate):

 def __init__(self, parent=None):
  super(PlainTextColumnDelegate, self).__init__(parent)


 def createEditor(self, parent, option, index):
  lineedit = QLineEdit(parent)
  return lineedit


 def setEditorData(self, editor, index):
  value = index.model().data(index, Qt.DisplayRole)
  editor.setText(value)


 def setModelData(self, editor, model, index):
  model.setData(index, editor.text())


class RichTextColumnDelegate(QStyledItemDelegate):

 def __init__(self, parent=None):
  super(RichTextColumnDelegate, self).__init__(parent)


 def paint(self, painter, option, index):
  text = index.model().data(index, Qt.DisplayRole)
  palette = QApplication.palette()
  document = QTextDocument()
  document.setDefaultFont(option.font)
  if option.state & QStyle.State_Selected:
   document.setHtml("<font color={0}>{1}</font>".format(palette.highlightedText().color().name(),text))
  else:
   document.setHtml(text)
  painter.save()
  color = (palette.highlight().color()
     if option.state & QStyle.State_Selected
     else QColor(index.model().data(index,
        Qt.BackgroundColorRole)))
  painter.fillRect(option.rect, color)
  painter.translate(option.rect.x(), option.rect.y())
  document.drawContents(painter)
  painter.restore()


 def sizeHint(self, option, index):
  text = index.model().data(index).toString()
  document = QTextDocument()
  document.setDefaultFont(option.font)
  document.setHtml(text)
  return QSize(document.idealWidth() + 5,
      option.fontMetrics.height())


 def createEditor(self, parent, option, index):
  lineedit = richtextlineedit.RichTextLineEdit(parent)
  return lineedit


 def setEditorData(self, editor, index):
  value = index.model().data(index, Qt.DisplayRole)
  editor.setHtml(value)


 def setModelData(self, editor, model, index):
  model.setData(index, editor.toSimpleHtml())

/home/yrd/eric_workspace/chap16/carhirelog.pyw

#!/usr/bin/env python3

import bisect
import os
import platform
import sys
from PyQt5.QtCore import (QAbstractTableModel, QDate, QModelIndex,
  QVariant, Qt,pyqtSignal)
from PyQt5.QtWidgets import (QApplication, QMainWindow,
  QShortcut, QTableView)
from PyQt5.QtGui import QKeySequence
import genericdelegates


(LICENSE, CUSTOMER, HIRED, MILEAGEOUT, RETURNED, MILEAGEBACK,
 NOTES, MILEAGE, DAYS) = range(9)


class CarHireLog(object):

 def __init__(self, license, customer, hired, mileageout,
     returned=QDate(), mileageback=0, notes=""):
  self.license = license  # plain text
  self.customer = customer # plain text
  self.hired = hired     # QDate
  self.mileageout = mileageout   # int
  self.returned = returned    # QDate
  self.mileageback = mileageback  # int
  self.notes = notes   # HTML


 def field(self, column):
  if column == LICENSE:
   return self.license
  elif column == CUSTOMER:
   return self.customer
  elif column == HIRED:
   return self.hired
  elif column == MILEAGEOUT:
   return self.mileageout
  elif column == RETURNED:
   return self.returned
  elif column == MILEAGEBACK:
   return self.mileageback
  elif column == NOTES:
   return self.notes
  elif column == MILEAGE:
   return self.mileage()
  elif column == DAYS:
   return self.days()
  assert False


 def mileage(self):
  return (0 if self.mileageback == 0
     else self.mileageback - self.mileageout)


 def days(self):
  return (0 if not self.returned.isValid()
     else self.hired.daysTo(self.returned))


 def __hash__(self):
  return super(CarHireLog, self).__hash__()


 def __eq__(self, other):
  if self.hired != other.hired:
   return False
  if self.customer != other.customer:
   return False
  if self.license != other.license:
   return False
  return id(self) == id(other)


 def __lt__(self, other):
  if self.hired < other.hired:
   return True
  if self.customer < other.customer:
   return True
  if self.license < other.license:
   return True
  return id(self) < id(other)


class CarHireModel(QAbstractTableModel):
 dataChanged = pyqtSignal(QModelIndex,QModelIndex)
 def __init__(self, parent=None):
  super(CarHireModel, self).__init__(parent)
  self.logs = []

  # Generate fake data
  import gzip
  import random
  import string
  surname_data = gzip.open(os.path.join(
    os.path.dirname(__file__), "surnames.txt.gz")).read()
  surnames = surname_data.decode("utf8").splitlines()
  years = ("06 ", "56 ", "07 ", "57 ", "08 ", "58 ")
  titles = ("Ms ", "Mr ", "Ms ", "Mr ", "Ms ", "Mr ", "Dr ")
  notetexts = ("Returned <font color=red><b>damaged</b></font>",
    "Returned with <i>empty fuel tank</i>",
    "Customer <b>complained</b> about the <u>engine</u>",
    "Customer <b>complained</b> about the <u>gears</u>",
    "Customer <b>complained</b> about the <u>clutch</u>",
    "Returned <font color=darkred><b>dirty</b></font>",)
  today = QDate.currentDate()
  for i in range(250):
   license = []
   for c in range(5):
    license.append(random.choice(string.ascii_uppercase))
   license = ("".join(license[:2]) + random.choice(years) +
      "".join(license[2:]))
   customer = random.choice(titles) + random.choice(surnames)
   hired = today.addDays(-random.randint(0, 365))
   mileageout = random.randint(10000, 30000)
   notes = ""
   if random.random() >= 0.2:
    days = random.randint(1, 21)
    returned = hired.addDays(days)
    mileageback = (mileageout +
        (days * random.randint(30, 300)))
    if random.random() > 0.75:
     notes = random.choice(notetexts)
   else:
    returned = QDate()
    mileageback = 0
   log = CarHireLog(license, customer, hired, mileageout,
        returned, mileageback, notes)
   bisect.insort(self.logs, log)


 def rowCount(self, index=QModelIndex()):
  return len(self.logs)


 def columnCount(self, index=QModelIndex()):
  return 9


 def data(self, index, role):
  if not index.isValid():
   return QVariant()
  if role == Qt.DisplayRole:
   log = self.logs[index.row()]
   value = log.field(index.column())
   if (index.column() in (MILEAGEBACK, MILEAGE, DAYS) and
    value == 0):
    return 0
   return value
  if (role == Qt.TextAlignmentRole and
   index.column() not in (LICENSE, CUSTOMER, NOTES)):
   return QVariant(int(Qt.AlignRight|Qt.AlignVCenter))
  if role == Qt.BackgroundColorRole:
   palette = QApplication.palette()
   if index.column() in (LICENSE, MILEAGE, DAYS):
    return QVariant(palette.alternateBase())
   else:
    return QVariant(palette.base())
  return QVariant()


 def setData(self, index, value, role=Qt.EditRole):
  if (index.isValid() and role == Qt.EditRole and
   index.column() not in (LICENSE, MILEAGE, DAYS)):
   log = self.logs[index.row()]
   column = index.column()
   if column == CUSTOMER:
    log.customer = value
   elif column == HIRED:
    #log.hired = value.toDate()
    log.hired = value
   elif column == MILEAGEOUT:
    log.mileageout = value
   elif column == RETURNED:
    #log.returned = value.toDate()
    log.returned = value
   elif column == MILEAGEBACK:
    log.mileageback = value
   elif column == NOTES:
    log.notes = value
   self.dataChanged[QModelIndex,QModelIndex].emit(index,index)
   return True
  return False


 def headerData(self, section, orientation, role):
  if role == Qt.TextAlignmentRole:
   if orientation == Qt.Horizontal:
    return QVariant(int(Qt.AlignCenter))
   return QVariant(int(Qt.AlignRight|Qt.AlignVCenter))
  if role != Qt.DisplayRole:
   return QVariant()
  if orientation == Qt.Horizontal:
   if section == LICENSE:
    return "License"
   elif section == CUSTOMER:
    return "Customer"
   elif section == HIRED:
    return "Hired"
   elif section == MILEAGEOUT:
    return "Mileage #1"
   elif section == RETURNED:
    return "Returned"
   elif section == MILEAGEBACK:
    return "Mileage #2"
   elif section == DAYS:
    return "Days"
   elif section == MILEAGE:
    return "Miles"
   elif section == NOTES:
    return "Notes"
  return section + 1


 def flags(self, index):
  flag = QAbstractTableModel.flags(self, index)
  if index.column() not in (LICENSE, MILEAGE, DAYS):
   flag |= Qt.ItemIsEditable
  return flag


class HireDateColumnDelegate(genericdelegates.DateColumnDelegate):

 def createEditor(self, parent, option, index):
  i = index.sibling(index.row(), RETURNED)
  self.maximum = i.model().data(i, Qt.DisplayRole).addDays(-1)
  return genericdelegates.DateColumnDelegate.createEditor(
    self, parent, option, index)


class ReturnDateColumnDelegate(genericdelegates.DateColumnDelegate):

 def createEditor(self, parent, option, index):
  i = index.sibling(index.row(), HIRED)
  self.minimum = i.model().data(i, Qt.DisplayRole).addDays(1)
  return genericdelegates.DateColumnDelegate.createEditor(
    self, parent, option, index)


class MileageOutColumnDelegate(genericdelegates.IntegerColumnDelegate):

 def createEditor(self, parent, option, index):
  i = index.sibling(index.row(), MILEAGEBACK)
  maximum = i.model().data(i, Qt.DisplayRole)
  self.maximum = 1000000 if maximum == 0 else maximum - 1
  return genericdelegates.IntegerColumnDelegate.createEditor(
    self, parent, option, index)


class MileageBackColumnDelegate(genericdelegates.IntegerColumnDelegate):

 def createEditor(self, parent, option, index):
  i = index.sibling(index.row(), MILEAGEOUT)
  self.minimum = i.model().data(i, Qt.DisplayRole) + 1
  return genericdelegates.IntegerColumnDelegate.createEditor(
    self, parent, option, index)


class MainForm(QMainWindow):

 def __init__(self, parent=None):
  super(MainForm, self).__init__(parent)

  model = CarHireModel(self)

  self.view = QTableView()
  self.view.setModel(model)
  self.view.resizeColumnsToContents()

  delegate = genericdelegates.GenericDelegate(self)
  delegate.insertColumnDelegate(CUSTOMER,
    genericdelegates.PlainTextColumnDelegate())
  earliest = QDate.currentDate().addYears(-3)
  delegate.insertColumnDelegate(HIRED,
    HireDateColumnDelegate(earliest))
  delegate.insertColumnDelegate(MILEAGEOUT,
    MileageOutColumnDelegate(0, 1000000))
  delegate.insertColumnDelegate(RETURNED,
    ReturnDateColumnDelegate(earliest))
  delegate.insertColumnDelegate(MILEAGEBACK,
    MileageBackColumnDelegate(0, 1000000))
  delegate.insertColumnDelegate(NOTES,
    genericdelegates.RichTextColumnDelegate())

  self.view.setItemDelegate(delegate)
  self.setCentralWidget(self.view)

  QShortcut(QKeySequence("Escape"), self, self.close)
  QShortcut(QKeySequence("Ctrl+Q"), self, self.close)

  self.setWindowTitle("Car Hire Logs")


app = QApplication(sys.argv)
form = MainForm()
rect = QApplication.desktop().availableGeometry()
form.resize(int(rect.width() * 0.7), int(rect.height() * 0.8))
form.move(0, 0)
form.show()
app.exec_()

运行结果：

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持【听图阁-专注于Python设计】。

返回列表

上一篇：Python字符转换

下一篇：PHP生成静态页面详解

相关文章

Django 实现外键去除自动添加的后缀‘_id’

django在使用外键ForeignKey的时候，会自动给当前字段后面添加一个后缀_id。 正常来说这样并不会影响使用。除非你要写原生sql，还有就是这个表是已经存在的，你只是把数据库中...

python如果快速判断数字奇数偶数

这篇文章主要介绍了python如果快速判断数字奇数偶数,文中通过示例代码介绍的非常详细，对大家的学习或者工作具有一定的参考学习价值,需要的朋友可以参考下 使用 按位与运算符(&) 将能更...

python异步存储数据详解

在Python中，数据存储方式分为同步存储和异步存储。同步写入速度比较慢，而爬虫速度比较快，有可能导致数据保存不完整，一部分数据没有入库。而异步可以将爬虫和写入数据库操作分开执行，互不影...

Python中线程的MQ消息队列实现以及消息队列的优点解析

“消息队列”是在消息的传输过程中保存消息的容器。消息队列管理器在将消息从它的源中继到它的目标时充当中间人。队列的主要目的是提供路由并保证消息的传递；如果发送消息时接收者不可用，消息队列会...

Python json模块使用实例

实际上JSON就是Python字典的字符串表示，但是字典作为一个复杂对象是无法直接传递,所以需要将其转换成字符串形式.转换的过程也是一种序列化过程. 用json.dumps序列化为jso...

© YiPeiWu.com 【宜配屋】 粤ICP备17031333号

Powered By Z-BlogPHP. Theme by TOYEAN.