Python · Scientific Computing & Data Science

What's the purpose of groupby in pandas, and what does a bare df.groupby("State") actually return?

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More in Scientific Computing & Data Science

You need to add two large sequences of numbers element by element, fast. Why is a NumPy ndarray faster than a Python list for this?

You want to compute x*3 - 4 for a million numbers in a. What's the idiomatic NumPy way, and what's the mistake to avoid?

What does this print? ``` import numpy as np a = np.array([1, 2, 3]) print(a + 10) ```

What does this print? ``` import numpy as np m = np.ones((3, 2)) v = np.array([10, 20]) print((m + v)[0]) ```

You try np.array([1,2,3]) + np.array([10,20]). What happens and why?

What does this print? ``` import numpy as np a = np.array([1, 2, 3]) a[0] = 7.9 print(a) ```

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