Usage

import turing

machine = turing.Machine(program, tape, h=0, s="0")
machine.run(steps=1e309, debug=False)
machine.count(tally="1")

Where program is a Turing machine program as below, tape is the initial state of the tape (e.g. if you want to represent 17 in unary, use tape = "1" * 17), h is the initial position of the head, and s is the initial state.

steps is the maximum number of steps that will be run (default is infinity). Multiple consecutive steps with the same parameters (same state and input) are called zoom steps, are more efficient, and count for 1/3 of a step.

machine.count() is optional and will count the number of consecutive 1s (or other specified mark) starting from the beginning of the tape. This is useful for working with unary.

0, "0", 1e309, False, and "1" are default values for arguments that can be omitted. If you create a machine without specifying program or tape, empty ones will be created.

Example: Doubling program

import turing

program = """
0 1 0 l 1  ; mark current 1 as 0, move left
1 _ 1 r 2  ; fill 1 in empty cell, move right
1 1 1 l 1  ; skip 1s moving left
2 0 1 r 0  ; restore currently marked 1, move to the next 1
2 1 1 r 2  ; skip 1s moving right
"""
tape = "1111"

turing.OPTIMIZE = False  # to see the full, pretty debug output
machine = turing.Machine(program, tape)
machine.run(debug=True)

Output:

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 0 1 1 1 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 0 1 1 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 0 1 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 0 1 1 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 0 1 1 _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 0 1 1 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 0 1 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 0 1 1 _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 0 1 _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 0 1 _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 0 _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ _ 1 1 1 1 1 1 1 0 _ _ _ _ _ _ _ _ _ _ _ _ _ _
_ _ _ _ _ _ _ 1 1 1 1 1 1 1 1 _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Result: 8 (11111111)

The amount of context (number of cells shown on either side of head) shown in the debug output defaults to 15 but can be changed with e.g: machine.context = 20