Session.pop方法的第二个参数在Python Flask中有什么作用? [英] What does the second argument of the Session.pop method do in Python Flask?

问题描述

我正在阅读Flask教程，只是想确切说明会话对象的.pop属性是做什么的，以及为什么它将采用无"参数.

I'm working through the Flask tutorial and would just like to clarify exactly what the .pop attr of the session object does and why it would take a 'None' parameter.

@app.route('/logout')
def logout():
    session.pop('logged_in', None)
    flash('You were logged out')
    return redirect(url_for('show_entries'))

推荐答案

根据 Flask的API 他们的 Session 类是python Dict 的包装.根据 Python文档中的 dict.pop():

According to Flask's API their Session class is a wrapper around a python Dict. According to the python documentation for dict.pop():

pop(键[，默认])

如果字典中有 key ，则将其删除并返回其值，否则返回 default .如果未提供 default ，并且字典中没有 key ，则会引发 KeyError .

If key is in the dictionary, remove it and return its value, else return default. If default is not given and key is not in the dictionary, a KeyError is raised.

在这种情况下，本教程要求您传入 None 作为默认值.

In this case the tutorial asks you to pass in None as the default value.

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