@saeedsadati I didn't catch you. Let me try to clarify. (1) In the beginning, there are (a) one library (actually a big python program max30100.py, which you import as a module), and (b) a test program (max30100_test.py, which you ran with all zero results), (2) Then I wrote two simple programs, (c) to read PartID, (d) to read PartID, temperature, and oximeter 4 times. Actually you can run (b) or (c) or (d) using the library (a).

Perhaps you can run (c) and (d), then you might understand better, and found things not so confusing.

My answer is on MAX30102 and a bit long winded. It would be nice if you can give your own answer here, using your MAX30100 board. I would suggest you to include the following: (a) How to i2cdetect device at 0x53, (b) How to i2cget PartID 0x15, (c) How to use python to read PartID, (4) How to use python to read (i) PartID, (ii) temperature, (iii) Oximeter 4 times, (iv) many ohter things you want to mess around.

@saeedsadati I know you are just a friendly oximeter newbie, but it is exactly an answer by a newbie talking in a newbie language that other future newbies can easily understand and therefore learning happily. There is actually too many MAX30100 tutorials in Arduino, but almost nothing in Rpi, so many Rpi MAC30100 newbies are now weeping in the dark. And your newbie answer is the "Real Thing" that would hopefully bring newbie joy to the Rpi world youtube.com/watch?v=oBm0X_lodh4

@saeedsadati Oh my goodness. You are going too fast! (1) mfitzp library is what I am planning to use in my next step. The whilemind library we are using are newbie friendly, therefore is good as a stepping stone. Next library we can try is mfitzp which is for ninja only, because it uses two advanced things (a) interrupt, (b) gpioZero. You need to convenience me that you know what are interrupt and gpioZero, to make sure I am not wasting my time talking ninja things to a know-nothing newbie.

(1) You original question uses the whilmind library. If you are switching to mfitzp without telling other newbies you have changed your mind, those stupid newbies would be confused and again go back to weep in the dark. So if you would like someone to entertain your advanced questions, you can doing many things: (2) Read Ref32 about StackFlow Collections and let me know if you understand what they are talking about, and let me have your comment about stackflow collections, ...

(3) This question is on whilemine only, so wfitzip/interrupt/gpioZero is OFF TOPIC. You may like to ask ANOTHER question and see if other ninjas come by and learn together. Ah, lunch time. See you later.