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Constructing Range and Ranges

You can create them from:

  1. strings
  2. range-like objects
  3. sequences of ints or these things, or other sequences
  4. explicitly, like you would create a range or slice

Essentially, the constructor has value and stop fields. If stop is provided then value is assumed to be the start, otherwise it's assumed you want to convert the value from something else.

Range from a string

from arranges import Range

# Create a range from a string. Like a slice but without the square brackets.
the_full_range = Range(":")  # an endless sequence starting at 0
the_empty_range = Range("")  # start, stop and len() are all 0
from_0_to_99 = Range("0:100")
skip_10_items = Range("10:")  # boundless, goes to infinity
access_by_index = Range("0")  # just the first item

# Decimal, hexadecimal, octal and binary are supported. Note that octal uses
# Python's 0o prefix, not 0 like in C.
gbc_palette = Range("0xff68:0xff88")
skip_bmp_header = Range("0o66:end")  # skip "54", "0x36" or "0b1100110" bytes

# "end" and "inf" are the same. You can also use "start" instead of 0.
the_full_range_again = Range("start:inf")

# whitespace is ignored during construction
first_kilobyte = Range("start : 0x400")

# They are simplified when converted to str, which they can be compared with.
assert first_kilobyte == ":1024"

# Comparisons work in both directions
assert "000001:000002" == Range("1")

# and the hash is the same as the string
w = Range("6 : 8")
assert hash(w) == hash("6:8")

# so you can use them as dict keys
d = {"6:8": "width"}
d[w] = "GIF file width"
assert d == {"6:8": "GIF file width"}

Ranges from a string

from arranges import Ranges

# You can put gaps in your range using commas.
pages_2_to_5_and_20 = Ranges("2:6, 20")

# The ranges are sorted and combined as they are added
overlapping = Ranges("start:10, 14, 1:3")
assert overlapping == ":10,14"

# But you can't hash Ranges because they're mutable
import pytest

with pytest.raises(ValueError):
    a = {overlapping: "whatever"}

Ranges from range-like objects

If it has a start, stop and step attribute then it quacks like a range so you can pass it in as the value. If the step value is something other than None or 1 then it'll raise ValueError.

from arranges import Range

from_slice = Range(slice(10, 20))
from_range = Range(range(10, 20))
from_other = Range(Range("10:20"))

assert from_slice == from_range == from_other == "10:20"

Ranges from sequences

When creating a Range object from a sequence, it'll have to be in sequential order with no gaps. Duplicates are absorbed.

from arranges import Range

l = list(range(100))
t = tuple(range(100))
i = (i for i in range(100))

assert Range(l) == Range(t) == Range(i) == ":100"

Ranges are much more forgiving:

from arranges import Ranges

jumble = Ranges([0, [2, 4], ["1:3"], 3, 4, range(10, 20)])

assert jumble == "5,10:20"

Explicitly creating a Range

You can create them in the same way as range or slice objects which have a slightly different syntax to slice notation.

from arranges import Range, inf

assert Range(10, inf) == "10:"

# Range("10") is not the same as Range(10)
assert Range(10) == ":10"
assert Range("10") == 10 == Range(10, 11)