Functional Programming in Python
map() 會讓 list 的每一個元素都會各自經過 func(x) 去處理，最後得到的會是一個新的數量相同的 list。
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MySQL system error codes
Print all OS error codes and MySQL error codes using the perror command.
Calculate the similarity of two vectors
You should only calculate Pearson Correlations when the number of items in common between two users is > 1, preferably greater than 5/10. Only calculate the Pearson Correlation for two users where they have commonly rated items.
Recommender System: Collaborative Filtering 協同過濾推薦演算法
dataset 會是 m 個用戶對 n 個物品的評分 utility matrix，因為通常只有部分用戶和部份物品會有評分資料，所以是一個 sparse matrix（稀疏矩陣）。目標是利用這些稀疏的資料去預測出用戶對他還沒評分過的物品的評分。
Simple Parallel Tasks in Python: concurrent.futures
concurrent.futures is well suited to Embarrassingly Parallel tasks. You could write concurrent code with a simple for loop.