Range in Python (1)

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*Memo:

• My post explains a range (2).
• My post explains range functions.
• My post explains a range shallow and deep copy.
• My post explains a list (1).
• My post explains a tuple (1).
• My post explains a set (1).
• My post explains a frozenset (1).
• My post explains a dictionary (1).
• My post explains an iterator (1).
• My post explains a string (1).
• My post explains a bytes (1).
• My post explains a bytearray (1).
• My post explains enumerate().
• My post explains zip().

A range:

• is the ordered immutable(hashable) collection of zero or more numbers whose type is range:
  • Ordered means that the order of the numbers in a range is kept so it guarantees that the order is always the same unless someone or something changes it.
  • Immutable(Hashable) means the numbers of a range cannot be changed.
• can be used with len() to get the length.
• is False if it's empty.
• can be checked if a specific number is in the range with in keyword.
• can be checked if the range is referred to by two variables with is keyword.
• and one or more ranges cannot be concatenated with + and |.
• cannot be enlarged with * and a number.
• can be iterated with a for statement.
• can be unpacked with an assignment and for statement, function and * but not with **.
• can be created by range().
• can be big because it's the special object which always uses small memory not to get MemoryError and it's not an iterator.
• can be read by indexing and slicing.
• cannot be changed by indexing, slicing and a del statement.
• can be continuously used through multiple variables.
• can be shallow-copied only by slicing but not by copy.copy().
• cannot be deep-copied and even shallow-copied by copy.deepcopy().

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Even a big range doesn't get MemoryError.

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range() can create a range between [start, stop) as shown below:

*Memo:

• The 1st argument is start or stop(Required-Type:int):
  • It's a start index(inclusive) or stop index(exclusive).
  • Don't use start= or stop=.
• The 2nd argument is stop(Optional-Type:int):
  • It's a stop index(exclusive).
  • Don't use stop=.
• The 3rd argument is step(Optional-Default:1-Type:int):
  • It's the interval of elements.
  • It cannot be 0.
  • Don't use step=.
• Only if one argument is set, the 1st argument is stop, creating the range between [0, stop).

# Empty range
v = range(0)
v = range(0, 0)
v = range(0, 0, 1)
v = range(5, 5)
v = range(5, 5, 1)
v = range(-10)
v = range(10, -10)
v = range(-10, 10, -3)
v = range(10, -10, 3)
# No error

v = range(5)
v = range(0, 5)
v = range(0, 5, 1)
v = range(-10, 10, 3)
v = range(10, -10, -3)
# No error

v = range(100000000)
print(len(range(5)))
for x in range(5): pass
v1, v2, v3 = range(3)
v1, *v2, v3 = range(6)
for v1, v2, v3 in [range(3), range(3, 6)]: pass
for v1, *v2, v3 in [range(6), range(6, 12)]: pass
print(*range(4), *range(4, 6))
print([*range(4), *range(4, 6)])
# No error

v = range(0, 5, 0)
v = range(3) + range(2) + range(4)
v = range(3) | range(2) | range(4)
v = range(5) * 3
# Error

A range is the ordered immutable(hashable) collection of zero or more numbers whose type is range as shown below:

*Memo:

• A range can be unpacked with *.
• A range can be read by indexing:
  • Indexing can be done with one or more [index] in the range [The 1st index, The last index]:
    • index(Required-Type:int):
      • Don't use index=.
    • Error occurs if index is out of range.
  • index can be signed indices(zero and positive and negative indices).

v = range(5)
v = range(0, 5)
v = range(0, 5, 1)

print(v)
# range(0, 5)

print(type(v))
# <class 'range'>

print(v.start, v.stop, v.step)
# 0 5 1

print(*v)
print(v[0], v[1], v[2], v[3], v[4])
print(v[-5], v[-4], v[-3], v[-2], v[-1])
# 0 1 2 3 4

v = range(0, 5, 0)
# ValueError: range() arg 3 must not be zero

# Empty range
v1 = range(0)
v2 = range(0, 0)
v3 = range(0, 0, 1)
v4 = range(5, 5)
v5 = range(5, 5, 1)

print(v1, v2, v3, v4, v5)
# range(0, 0) range(0, 0) range(0, 0) range(5, 5) range(5, 5)

print(v[0])
# IndexError: range object index out of range

v = range(-10, 10, 3)

print(v)
# range(-10, 10, 3)

print(*v)
print(v[0], v[1], v[2], v[3], v[4], v[5], v[6])
print(v[-7], v[-6], v[-5], v[-4], v[-3], v[-2], v[-1])
# -10 -7 -4 -1 2 5 8

v = range(10, -10, -3)

print(v)
# range(10, -10, -3)

print(*v)
print(v[0], v[1], v[2], v[3], v[4], v[5], v[6])
print(v[-7], v[-6], v[-5], v[-4], v[-3], v[-2], v[-1])
# 10 7 4 1 -2 -5 -8

v1 = range(-10)
v2 = range(10, -10)
v3 = range(-10, 10, -3)
v4 = range(10, -10, 3)

print(v1, v2, v3, v4)
# range(0, -10) range(10, -10) range(-10, 10, -3) range(10, -10, 3)

print(v1[0])
print(v2[0])
print(v3[0])
print(v4[0])
# IndexError: range object index out of range

A range can be used with len() to get the length as shown below:

v = range(5)

print(*v)
# 0 1 2 3 4

print(len(v))
# 5