CODEWITHSUNDEEP
pythonpython-idle
Neitsa
Neitsa

Reputation: 8176

Changing number representation in IDLE

I use Python IDLE a lot in my day-to-day job, mostly for short scripts and as a powerful and convenient calculator.

I usually have to work with different numeric bases (mostly decimal, hexadecimal, binary and less frequently octal and other bases.)

I know that using int(), hex(), bin(), oct() is a convenient way to move from one base to another and prefixing integer literals with the right prefix is another way to express an number.

I find it quite inconvenient to have to put a calculation in a function just to see the result in the right base (and the resulting ouput of hex() and similar functions is a string) , so what I'm trying to achieve is to have either a function (or maybe a statement?) that set the internal IDLE number representation to a known base (2, 8, 10, 16).

Example :

>>> repr_hex() # from now on, all number are considered hexadecimal, in input and in output

>>> 10 # 16 in dec
>>> 0x10 # now output is also in hexadecimal

>>> 1e + 2 
>>> 0x20

# override should be possible with integer literal prefixes
# 0x: hex ; 0b: bin ; 0n: dec ; 0o: oct
>>> 0b111 + 10 + 0n10 # dec : 7 + 16 + 10
>>> 0x21 # 33 dec

# still possible to override output representation temporarily with a conversion function
>>> conv(_, 10) # conv(x, output_base, current_base=internal_base)
>>> 0n33
>>> conv(_, 2) # use prefix of previous output to set current_base to 10
>>> 0b100001
>>> conv(10, 8, 16) # convert 10 to base 8 (10 is in base 16: 0x10)
>>> 0o20

>>> repr_dec() # switch to base 10, in input and in output
>>> _
>>> 0n16
>>> 10 + 10
>>> 0n20

Implementing those features doesn't seem to be difficult, what I don't know is:

Thank you.

Upvotes: 2

Views: 960

Answers (1)

Terry Jan Reedy
Terry Jan Reedy

Reputation: 19174

IDLE does not have a number representation. It sends the code you enter to a Python interpreter and displays the string sent back in response. In this sense, it is irrelevant that IDLE is written in Python. The same is true of any IDE or REPL for Python code.

That said, the CPython sys module has a displayhook function. For 3.5:

>>> help(sys.displayhook)
Help on built-in function displayhook in module sys:

displayhook(...)
    displayhook(object) -> None

    Print an object to sys.stdout and also save it in builtins._

That actually should be __builtins__._, as in the example below. Note that the input is any Python object. For IDLE, the default sys.displayhook is a function defined in idlelib/rpc.py. Here is an example relevant to your question.

>>> def new_hook(ob):
    if type(ob) is int:
        ob = hex(ob)
    __builtins__._ = ob
    print(ob)


>>> sys.displayhook = new_hook
>>> 33
0x21
>>> 0x21
0x21

This gives you the more important half of what you asked for. Before actually using anything in IDLE, I would look at the default version to make sure I did not miss anything. One could write an extension to add menu entries that would switch displayhooks.

Python intentionally does not have an input preprocessor function. GvR wants the contents of a .py file to always be python code as defined in some version of the reference manual.

I have thought about the possibility of adding an inputhook to IDLE, but I would not allow one to be active when running a .py file from the editor. If there were one added for the Shell, I would change the prompt from '>>>' to something else, such as 'hex>' or 'bin>'.

EDIT: One could also write an extension to rewrite input code when explicitly requested either with a menu selection or a hot key or key binding. Or one could edit the current idlelib/ScriptBinding.py to make rewriting automatic. The hook I have thought about would make this easier, but not expand what can be done now.

Upvotes: 5

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