Python Thinking

Yes, it's commonplace to use a list comprehension instead of a "for" loop like you show. More generally, if you'd ever write

l = []
for x in someiterator:
  l.append(f(x))

l = [f(x) for x in someiterator]

This is shorter and apparently an imperceptibly tiny bit faster. If you're using an aggressive linter setup, the perflint W8401 warning or the equivalent Ruff PERF401 error will recomment using the list-comprehension syntax.

I don't understand what is the problem. But both code do the same. Some people prefers first version with normal for-loop, other prefer list comprehensions. Normal for-loops allows to add something more in loop - ie. print() for primitive debugging.

yeah, there's nothing "old fashioned" about OP's approach… not being aware of the second one just mean's the asker isn't very experienced at Python. List comprehensions have been around since Python 2.0, so October 2000, 25 years ago. They're fairly ubiquitous in code that has been written since then. There's nothing "newfangled" about [np.random.randint(min,max,) for _ in range(length)].

The second solution is using a list comprehension to achieve the same objective as your original solution. Both produce the same result.

List comprehensions such as the example shown here is concise and most Python programmers will understand what's going on at a glance.

However, some people take list comprehensions too far - i.e., they're very complex and hence difficult to read / maintain.

Your "old fashioned" approach is perfectly reasonable and arguably easier to understand if Python is not your main area of expertise.

You probably haven't encountered functional programming before. The following comprehensions may be of interest to you:

import random
generator
def generaterandomgen(minvalue, maxvalue, length):
    return (random.randint(minvalue, maxvalue) for  in range(length))
gen = generaterandomgen(0, 3, 10)
print([next(gen) for  in range(5)], [next(gen) for  in range(5)])
set comprehension
def generaterandomset(minvalue, maxvalue, length):
    return {random.randint(minvalue, maxvalue) for  in range(length)}
print(generaterandomset(0, 3, 100))
dict comprehension
def generaterandomdict(minvalue, maxvalue, length):
    return {i: random.randint(minvalue, maxvalue) for i in range(length)}
print(generaterandomdict(0, 3, 10))

Output:

[3, 3, 0, 2, 2] [2, 1, 1, 1, 0]
{0, 1, 2, 3}
{0: 3, 1: 1, 2: 2, 3: 2, 4: 3, 5: 0, 6: 0, 7: 1, 8: 3, 9: 0}

One thing to note, is that list comprehensions tend to be faster than using for loops.