Python

• Count specific elements in list: len([x for x in mylist if x==value])

• Create a 2D matrix: Matrix = [ [0 for x in range(cols)] for y in range(rows)] Ref. element in row i, col j: Matrix[i][j]

• Initialize a list with a map function: map( lambda x: x+1, range(3) ) ==> [1, 2, 3]

• a list of n zeros: [0] * n

• exchange values of two vars: a, b = b, a

• *, **

git

• Squash (already pushed) 3 commits: git rebase -i upstream/onboarding~3 onboarding (watch the tilde ~) (replace pick with fixup) git push -u upstream +onboarding (watch the +) more: https://stackoverflow.com/questions/5667884/how-to-squash-commits-in-git-after-they-have-been-pushed