Python · Scientific Computing & Data Science

How do you save a pandas DataFrame to CSV and read one back, and what's the gotcha with Excel files?

Answer locked. Get the free KnowCard app to reveal it — plus spaced-repetition review so it actually sticks.

This is one card from the KnowCard library — thousands more across SAP, Linux, Python and more. In the app you get the answer, AI explanations, and cards that come back right before you would forget them. Free to start on iOS, Android or the web.

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) ```

Start learning today

Free to start — download the app or use it in your browser.