Python: elif statements using list comprehension

Question

Lets take the next reproducible example:

I have a numpy array with a sequence of datetime.datetime elements in an hourly frequency,
From that array, I want to create a list datesVect which I want to be True for datetimes between Februrary and April and else False.

following the validated answer of this question and the explanation of the usage of list comprehension conditionals of this post I try to do it with the following code:

import numpy as np
import datetime

#Setting the startdate and creating the data range array:

startDate = datetime.datetime(2023,1,1)
dateHour = np.array([startDate + datetime.timedelta(0,3600*n) for n in range(8760)])

#Creating the desired list

datesVect = [True if j.month < 5 else True if j.month > 1 else False for j in dateHour]

Instead of getting the desired result I get a list full of True values:

In [211]: all(datesVect)
Out[211]: True

Anyone knows why I don’t get the desired result?

Asked By: Mauro

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Source

Answer 1

I recommend to just use the and operator. Your current code is functioning similar to the or operator, hence why you get an array of all True values. To be between Feb and April the month must be greater than 1 and less than 5.

datesVect = [True if (j.month < 5 and j.month > 1) else False for j in dateHour]

Answered By: Sterling

Python: elif statements using list comprehension

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