This is the behaviour to adopt when the referenced object is deleted. It is not specific to Django; this is an SQL standard. Although Django has its own implementation on top of SQL. (1) There are seven possible actions to take when such event occurs: CASCADE: When the referenced object is deleted, also delete the objects that have … Read more
The syntax a if b else c is a ternary operator in Python that evaluates to a if the condition b is true – otherwise, it evaluates to c. It can be used in comprehension statements: So for your example,
I’m quite sure, that the internet is full of python while-loops, but one example:
You ran one line, not the whole file. You can see the problem by carefully reading the traceback. Line 9 in the script is line 1 in the traceback: —-> 1 plt.show() The solution is to run the whole file not one line, i.e. click Run All not Run.
If you don’t care about data: Best way would be to drop the database and run syncdb again. Or you can run: For Django >= 1.5 For Django < 1.5 (you can add –no-input to the end of the command for it to skip the interactive prompt.) If you do care about data: From the docs: syncdb will only … Read more
The method len() returns the number of elements in the list. Syntax: Eg: Output:
Your approach will work despite the warning, but it’s best not to rely on implicit, unclear behavior. Solution 1, make the selection of indices in a_list a boolean mask: Solution 2, do it in two steps: Solution 3, if you want a one-liner, use a trick found here: The warning comes from the fact that the boolean vector df.a_col.isnull() is … Read more
Your replace format is off
>> reverse([1,2,3,4,5]) [5, 4, 3, 2, 1]
After that you can check it by: As an output you will see: 2