WhyCan Forum(哇酷开发者社区)

 
# Line892 @matplotlib/_init_.py
class RcParams(MutableMapping, dict):
    ...
    def __getitem__(self, key):
        ...
       elif key == "backend":
            val = dict.__getitem__(self, key)
            if val is rcsetup._auto_backend_sentinel:
                from matplotlib import pyplot as plt
                plt.switch_backend(rcsetup._auto_backend_sentinel)

# Line177 @matplotlib/pyplot.py
def switch_backend(newbackend):
    """
    Close all open figures and set the Matplotlib backend.

    The argument is case-insensitive.  Switching to an interactive backend is
    possible only if no event loop for another interactive backend has started.
    Switching to and from non-interactive backends is always possible.

    Parameters
    ----------
    newbackend : str
        The name of the backend to use.
    """
    close("all")

    if newbackend is rcsetup._auto_backend_sentinel:
        for candidate in ["macosx", "qt5agg", "qt4agg", "gtk3agg", "gtk3cairo",
                          "tkagg", "wxagg", "agg", "cairo"]:
            try:
                switch_backend(candidate)
            except ImportError:
                continue
            else:
                rcParamsOrig['backend'] = candidate
                return
    ....