Dictionaries have a method called items that returns a list of tuples, where each tuple is a key-value pair. As you should expect from a dictionary, the items are in no particular order. Conversely, you can use a list of tuples to initialize a new di…
12.1 Tuples are immutable(元组是不可变的)A tuple is a sequence of values. The values can be any type, and they are indexed by integers, so in that respect tuples are a lot like lists. The important difference is that tuples are immutable.Syntactically, a tu…
Item 22: Prefer Helper Classes Over Bookkeeping with Dictionaries and Tuples For example, say you want to record the grades of a set of students whose names aren't konwn in advance. You can define a class to store the names in a dictionary instead of…
17.1 Object-oriented featuresPython is an object-oriented programming language, which means that it provides features that support object-oriented programming.It is not easy to define object-oriented programming, but we have already seen some of its…
Python is an object-oriented programing language, which means that it provides features that support object-oriented programming. It is easy to define object-oriented programming, but we have already seen some of its characteristics: Programs are mad…
Operations upon Impala Create table stored as parquet like parquet '/user/etl/datafile1' stored as parquet Loading data shuffle / no shuffle to choose 使用insert ... select 而不是 insert ... values, 因为后者产生a separate tiny data file. impala decodes the colu…
