list comprehension, how to append the new elements to the list?

am working on my Python assessment and I need a hand :( so, the task is to use this equation: 10*x-5 and print positive numbers only; the task focuses on using list comprehension, finally, I’ve to print the updated list. I did all of that but i couldn’t figure out how to insert/append the updated elements to the new list, so here is what’ve done..

lst =[]
Update_MyList = [lst.append(MyList[z])for z in range(len(MyList)) if (10*MyList[z]-5 > 0)]
Update_MyList.append(lst)
print(Update_MyList)

all what I get is:[None, None, None, None, None]

Answer

Code1

Assuming your MyList is [1, -2, 3] and you want to print None when output is negative. Here’s a code1:

MyList = [1, -2, 3]

Update_MyList = [10*x-5 if (10*x-5 > 0) else None for x in MyList]

print(Update_MyList)

Output:

[5, None, 25]

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After Edit

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Code 2

If you don’t want None for negative values, just remove else None part. Here’s a code2:

MyList = [1, -2, 3]

Update_MyList = [10*x-5 if (10*x-5 > 0) for x in MyList]

print(Update_MyList)

Output:

[5, 25]

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Code 3

If you are using python>=3.8, use the below code to avoid calculating 10*x-5 twice. Here’s a code3:

MyList = [1, -2, 3]

Update_MyList = [y for x in MyList if (y := 10*x-5) > 0]

print(Update_MyList)

Output:

[5, 25]