How to define a two-dimensional array?

You’re technically trying to index an uninitialized array. You have to first initialize the outer list with lists before adding items; Python calls this “list comprehension”. #You can now add items to the list: Note that the matrix is “y” address major, in other words, the “y index” comes before the “x index”. Although you … Read more

What does ‘–set-upstream’ do?

To avoid confusion,recent versions of git deprecate this somewhat ambiguous –set-upstream optionin favor of a more verbose –set-upstream-to optionwith identical syntax and behavior. sets the default remote branch for the current local branch. Any future git pull command (with the current local branch checked-out),will attempt to bring in commits from the <remote-branch> into the current local branch. One way to avoid having to explicitly type –set-upstream / –set-upstream-to is … Read more

Iterating over dictionaries using ‘for’ loops

key is just a variable name. will simply loop over the keys in the dictionary, rather than the keys and values. To loop over both key and value you can use the following: For Python 3.x: For Python 2.x: To test for yourself, change the word key to poop. In Python 3.x, iteritems() was replaced with simply items(), which returns a set-like … Read more

Understanding slice notation

It’s pretty simple really: There is also the step value, which can be used with any of the above: The key point to remember is that the :stop value represents the first value that is not in the selected slice. So, the difference between stop and start is the number of elements selected (if step is 1, the default). The other feature is that start or stop may be a negative number, which … Read more

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