PyQt5之QApplication和QWidget
app = QApplication(sys.argv)
每一个PyQt5程序都需要有一个QApplication对象。sys.argv是从命令行传入的参数列表。Python脚本可以从shell中运行。这是一种通过参数来选择启动脚本的方式。
window = QWidget()
QWidget控件是PyQt5中所有用户界面的父类，QWidget对象创建成为一个应用的顶层窗口。这里使用了没有参数的默认构造函数，它没有父类，我们称没有父类的控件为窗口。
由于所有的窗口和控件都是继承与QWidget类，所以如果不为控件指定一个父对象，那么控件就会呗当作窗口处理，这时setWindowTitle（）和setWindowIcon()函数就会生效
方法如下，详细使用方法可以看官网链接https://doc.qt.io/qt-5/qwidget.html
Public Functions
| QWidget(QWidget *parent = nullptr, Qt::WindowFlags f = ...) | |
| virtual | ~QWidget() |
| bool | acceptDrops() const |
| QString | accessibleDescription() const |
| QString | accessibleName() const |
| QList |
actions() const |
| void | activateWindow() |
| void | addAction(QAction *action) |
| void | addActions(QList |
| void | adjustSize() |
| bool | autoFillBackground() const |
| QPalette::ColorRole | backgroundRole() const |
| QBackingStore * | backingStore() const |
| QSize | baseSize() const |
| QWidget * | childAt(int x, int y) const |
| QWidget * | childAt(const QPoint &p) const |
| QRect | childrenRect() const |
| QRegion | childrenRegion() const |
| void | clearFocus() |
| void | clearMask() |
| QMargins | contentsMargins() const |
| QRect | contentsRect() const |
| Qt::ContextMenuPolicy | contextMenuPolicy() const |
| QCursor | cursor() const |
| WId | effectiveWinId() const |
| void | ensurePolished() const |
| Qt::FocusPolicy | focusPolicy() const |
| QWidget * | focusProxy() const |
| QWidget * | focusWidget() const |
| const QFont & | font() const |
| QFontInfo | fontInfo() const |
| QFontMetrics | fontMetrics() const |
| QPalette::ColorRole | foregroundRole() const |
| QRect | frameGeometry() const |
| QSize | frameSize() const |
| const QRect & | geometry() const |
| void | getContentsMargins(int *left, int *top, int *right, int *bottom) const |
| QPixmap | grab(const QRect &rectangle = QRect(QPoint(0, 0), QSize(-1, -1))) |
| void | grabGesture(Qt::GestureType gesture, Qt::GestureFlags flags = ...) |
| void | grabKeyboard() |
| void | grabMouse() |
| void | grabMouse(const QCursor &cursor) |
| int | grabShortcut(const QKeySequence &key, Qt::ShortcutContext context = Qt::WindowShortcut) |
| QGraphicsEffect * | graphicsEffect() const |
| QGraphicsProxyWidget * | graphicsProxyWidget() const |
| bool | hasEditFocus() const |
| bool | hasFocus() const |
| virtual bool | hasHeightForWidth() const |
| bool | hasMouseTracking() const |
| bool | hasTabletTracking() const |
| int | height() const |
| virtual int | heightForWidth(int w) const |
| Qt::InputMethodHints | inputMethodHints() const |
| virtual QVariant | inputMethodQuery(Qt::InputMethodQuery query) const |
| void | insertAction(QAction *before, QAction *action) |
| void | insertActions(QAction *before, QList |
| bool | isActiveWindow() const |
| bool | isAncestorOf(const QWidget *child) const |
| bool | isEnabled() const |
| bool | isEnabledTo(const QWidget *ancestor) const |
| bool | isFullScreen() const |
| bool | isHidden() const |
| bool | isMaximized() const |
| bool | isMinimized() const |
| bool | isModal() const |
| bool | isVisible() const |
| bool | isVisibleTo(const QWidget *ancestor) const |
| bool | isWindow() const |
| bool | isWindowModified() const |
| QLayout * | layout() const |
| Qt::LayoutDirection | layoutDirection() const |
| QLocale | locale() const |
| QPoint | mapFrom(const QWidget *parent, const QPoint &pos) const |
| QPoint | mapFromGlobal(const QPoint &pos) const |
| QPoint | mapFromParent(const QPoint &pos) const |
| QPoint | mapTo(const QWidget *parent, const QPoint &pos) const |
| QPoint | mapToGlobal(const QPoint &pos) const |
| QPoint | mapToParent(const QPoint &pos) const |
| QRegion | mask() const |
| int | maximumHeight() const |
| QSize | maximumSize() const |
| int | maximumWidth() const |
| int | minimumHeight() const |
| QSize | minimumSize() const |
| virtual QSize | minimumSizeHint() const |
| int | minimumWidth() const |
| void | move(const QPoint &) |
| void | move(int x, int y) |
| QWidget * | nativeParentWidget() const |
| QWidget * | nextInFocusChain() const |
| QRect | normalGeometry() const |
| void | overrideWindowFlags(Qt::WindowFlags flags) |
| const QPalette & | palette() const |
| QWidget * | parentWidget() const |
| QPoint | pos() const |
| QWidget * | previousInFocusChain() const |
| QRect | rect() const |
| void | releaseKeyboard() |
| void | releaseMouse() |
| void | releaseShortcut(int id) |
| void | removeAction(QAction *action) |
| void | render(QPaintDevice *target, const QPoint &targetOffset = QPoint(), const QRegion &sourceRegion = QRegion(), QWidget::RenderFlags renderFlags = ...) |
| void | render(QPainter *painter, const QPoint &targetOffset = QPoint(), const QRegion &sourceRegion = QRegion(), QWidget::RenderFlags renderFlags = ...) |
| void | repaint(int x, int y, int w, int h) |
| void | repaint(const QRect &rect) |
| void | repaint(const QRegion &rgn) |
| void | resize(const QSize &) |
| void | resize(int w, int h) |
| bool | restoreGeometry(const QByteArray &geometry) |
| QByteArray | saveGeometry() const |
| void | scroll(int dx, int dy) |
| void | scroll(int dx, int dy, const QRect &r) |
| void | setAcceptDrops(bool on) |
| void | setAccessibleDescription(const QString &description) |
| void | setAccessibleName(const QString &name) |
| void | setAttribute(Qt::WidgetAttribute attribute, bool on = true) |
| void | setAutoFillBackground(bool enabled) |
| void | setBackgroundRole(QPalette::ColorRole role) |
| void | setBaseSize(const QSize &) |
| void | setBaseSize(int basew, int baseh) |
| void | setContentsMargins(int left, int top, int right, int bottom) |
| void | setContentsMargins(const QMargins &margins) |
| void | setContextMenuPolicy(Qt::ContextMenuPolicy policy) |
| void | setCursor(const QCursor &) |
| void | setEditFocus(bool enable) |
| void | setFixedHeight(int h) |
| void | setFixedSize(const QSize &s) |
| void | setFixedSize(int w, int h) |
| void | setFixedWidth(int w) |
| void | setFocus(Qt::FocusReason reason) |
| void | setFocusPolicy(Qt::FocusPolicy policy) |
| void | setFocusProxy(QWidget *w) |
| void | setFont(const QFont &) |
| void | setForegroundRole(QPalette::ColorRole role) |
| void | setGeometry(const QRect &) |
| void | setGeometry(int x, int y, int w, int h) |
| void | setGraphicsEffect(QGraphicsEffect *effect) |
| void | setInputMethodHints(Qt::InputMethodHints hints) |
| void | setLayout(QLayout *layout) |
| void | setLayoutDirection(Qt::LayoutDirection direction) |
| void | setLocale(const QLocale &locale) |
| void | setMask(const QBitmap &bitmap) |
| void | setMask(const QRegion ®ion) |
| void | setMaximumHeight(int maxh) |
| void | setMaximumSize(const QSize &) |
| void | setMaximumSize(int maxw, int maxh) |
| void | setMaximumWidth(int maxw) |
| void | setMinimumHeight(int minh) |
| void | setMinimumSize(const QSize &) |
| void | setMinimumSize(int minw, int minh) |
| void | setMinimumWidth(int minw) |
| void | setMouseTracking(bool enable) |
| void | setPalette(const QPalette &) |
| void | setParent(QWidget *parent) |
| void | setParent(QWidget *parent, Qt::WindowFlags f) |
| void | setShortcutAutoRepeat(int id, bool enable = true) |
| void | setShortcutEnabled(int id, bool enable = true) |
| void | setSizeIncrement(const QSize &) |
| void | setSizeIncrement(int w, int h) |
| void | setSizePolicy(QSizePolicy) |
| void | setSizePolicy(QSizePolicy::Policy horizontal, QSizePolicy::Policy vertical) |
| void | setStatusTip(const QString &) |
| void | setStyle(QStyle *style) |
| void | setTabletTracking(bool enable) |
| void | setToolTip(const QString &) |
| void | setToolTipDuration(int msec) |
| void | setUpdatesEnabled(bool enable) |
| void | setWhatsThis(const QString &) |
| void | setWindowFilePath(const QString &filePath) |
| void | setWindowFlag(Qt::WindowType flag, bool on = true) |
| void | setWindowFlags(Qt::WindowFlags type) |
| void | setWindowIcon(const QIcon &icon) |
| void | setWindowModality(Qt::WindowModality windowModality) |
| void | setWindowOpacity(qreal level) |
| void | setWindowRole(const QString &role) |
| void | setWindowState(Qt::WindowStates windowState) |
| void | setupUi(QWidget *widget) |
| QSize | size() const |
| virtual QSize | sizeHint() const |
| QSize | sizeIncrement() const |
| QSizePolicy | sizePolicy() const |
| void | stackUnder(QWidget *w) |
| QString | statusTip() const |
| QStyle * | style() const |
| QString | styleSheet() const |
| bool | testAttribute(Qt::WidgetAttribute attribute) const |
| QString | toolTip() const |
| int | toolTipDuration() const |
| bool | underMouse() const |
| void | ungrabGesture(Qt::GestureType gesture) |
| void | unsetCursor() |
| void | unsetLayoutDirection() |
| void | unsetLocale() |
| void | update(int x, int y, int w, int h) |
| void | update(const QRect &rect) |
| void | update(const QRegion &rgn) |
| void | updateGeometry() |
| bool | updatesEnabled() const |
| QRegion | visibleRegion() const |
| QString | whatsThis() const |
| int | width() const |
| WId | winId() const |
| QWidget * | window() const |
| QString | windowFilePath() const |
| Qt::WindowFlags | windowFlags() const |
| QWindow * | windowHandle() const |
| QIcon | windowIcon() const |
| Qt::WindowModality | windowModality() const |
| qreal | windowOpacity() const |
| QString | windowRole() const |
| Qt::WindowStates | windowState() const |
| QString | windowTitle() const |
| Qt::WindowType | windowType() const |
| int | x() const |
| int | y() const |
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