Python Forum

why is range() int only? why did they not allow it to work with float and decimal ... at least with all args the same type?

I guess the reason is historical. Also it avoids type checking in a heavily used function. numpy.arange() supports several data types.

Because range is used for indexing and if you need to address an element in a sequence, you need integers.
But you've all tools to build your own range:

def arange(start_or_end, end=None, step=1):
    if end is None:
        start_or_end, end = 0, start_or_end

    value = start_or_end

    while value < end:
        yield value
        value += step

Testing with Decimal:

from decimal import Decimal


for dec in arange(Decimal(0), Decimal(5), Decimal("0.25")):
    print(dec)

Output:
0
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
2.75
3.00
3.25
3.50
3.75
4.00
4.25
4.50
4.75

Testing with Fraction:

from fractions import Fraction


for frac in arange(Fraction(0), Fraction(5), Fraction(1, 3)):
    print(frac)

Output:
0
1/3
2/3
1
4/3
5/3
2
7/3
8/3
3
10/3
11/3
4
13/3
14/3

Testing with float:

from decimal import Decimal


for real in arange(0, 5, 0.25):
    print(real)

Output:
0
0.25
0.5
0.75
1.0
1.25
1.5
1.75
2.0
2.25
2.5
2.75
3.0
3.25
3.5
3.75
4.0
4.25
4.5
4.75

the indexing use case being so dominant does not rule out other use cases. but a concise efficient implementation in C might be the reason. it does type check, and other checks. if it is in C then a type check is probably essential to avoid memory corruption that C is infamous for. i played around with implementing my own. it does reverse decrements, too. i have only tested floats. but it looks like numpy will be in my float use case. or i might scale the ints.