在python中用matplotlab画图，显示

RuntimeError: The environment variable QT_API has the unrecognized value '5.12.0'; valid values are pyqt6, pyside6, pyqt5, pyside2

在错误信息的最后一条

File "D:develop_toolspythonlibsite-packagesmatplotlibackendsqt_compat.py", line 67, in <module>

打开错误信息提到的qt_compat.py

if sys.modules.get("PyQt6.QtCore"):
    QT_API = QT_API_PYQT6
elif sys.modules.get("PySide6.QtCore"):
    QT_API = QT_API_PYSIDE6
elif sys.modules.get("PyQt5.QtCore"):
    QT_API = QT_API_PYQT5
elif sys.modules.get("PySide2.QtCore"):
    QT_API = QT_API_PYSIDE2
# Otherwise, check the QT_API environment variable (from Enthought).  This can
# only override the binding, not the backend (in other words, we check that the
# requested backend actually matches).  Use _get_backend_or_none to avoid
# triggering backend resolution (which can result in a partially but
# incompletely imported backend_qt5).
elif (mpl.rcParams._get_backend_or_none() or "").lower().startswith("qt5"):
    if QT_API_ENV in ["pyqt5", "pyside2"]:
        QT_API = _ETS[QT_API_ENV]
    else:
        _QT_FORCE_QT5_BINDING = True  # noqa
        QT_API = None
# A non-Qt backend was selected but we still got there (possible, e.g., when
# fully manually embedding Matplotlib in a Qt app without using pyplot).
elif QT_API_ENV is None:
    QT_API = None
elif QT_API_ENV in _ETS:
    QT_API = _ETS[QT_API_ENV]
else:
    raise RuntimeError(                                               #67行
        "The environment variable QT_API has the unrecognized value {!r}; "
        "valid values are {}".format(QT_API_ENV, ", ".join(_ETS)))

本机装了PyQt5，上方代码中

elif sys.modules.get("PyQt5.QtCore"):
    QT_API = QT_API_PYQT5

应该没有执行

查看 sys.modules 的功能

python中的sys.modules是一个全局字典，从python程序启动就加载到了内存，用于保存当前已导入(加载)的所有模块名和模块对象

应该是PyQt5.QtCore没有导入，导致没有执行这个elif

不知怎样，直接在if上方添加导入的import PyQt5.QtCore

import PyQt5.QtCore          #加入
if sys.modules.get("PyQt6.QtCore"):
    QT_API = QT_API_PYQT6
elif sys.modules.get("PySide6.QtCore"):
    QT_API = QT_API_PYSIDE6
elif sys.modules.get("PyQt5.QtCore"):
    QT_API = QT_API_PYQT5

保存文件。
重新画图，暂时运行正常。