Python Programmatically Change Console font size

Before everything, check [SO]: C function called from Python via ctypes returns incorrect value (@CristiFati’s answer) for a common pitfall when working with CTypes (calling functions).

The CTypes home page (also listed in the above URL): [Python.Docs]: ctypes – A foreign function library for Python

I changed your code "a bit".

code00.py:

#!/usr/bin/env python

import ctypes as cts
import ctypes.wintypes as wts
import sys


LF_FACESIZE = 32
STD_OUTPUT_HANDLE = -11


class CONSOLE_FONT_INFOEX(cts.Structure):
    _fields_ = (
        ("cbSize", wts.ULONG),
        ("nFont", wts.DWORD),
        ("dwFontSize", wts._COORD),
        ("FontFamily", wts.UINT),
        ("FontWeight", wts.UINT),
        ("FaceName", wts.WCHAR * LF_FACESIZE)
    )


def main(*argv):
    kernel32 = cts.WinDLL("Kernel32.dll")

    GetLastError = kernel32.GetLastError
    GetLastError.argtypes = ()
    GetLastError.restype = wts.DWORD

    GetStdHandle = kernel32.GetStdHandle
    GetStdHandle.argtypes = (wts.DWORD,)
    GetStdHandle.restype = wts.HANDLE

    GetCurrentConsoleFontEx = kernel32.GetCurrentConsoleFontEx
    GetCurrentConsoleFontEx.argtypes = (wts.HANDLE, wts.BOOL, cts.POINTER(CONSOLE_FONT_INFOEX))
    GetCurrentConsoleFontEx.restype = wts.BOOL

    SetCurrentConsoleFontEx = kernel32.SetCurrentConsoleFontEx
    SetCurrentConsoleFontEx.argtypes = (wts.HANDLE, wts.BOOL, cts.POINTER(CONSOLE_FONT_INFOEX))
    SetCurrentConsoleFontEx.restype = wts.BOOL

    # Get stdout handle
    stdout = GetStdHandle(STD_OUTPUT_HANDLE)
    if not stdout:
        print("{:s} error: {:d}".format(GetStdHandle.__name__, GetLastError()))
        return
    # Get current font characteristics
    font = CONSOLE_FONT_INFOEX()
    font.cbSize = cts.sizeof(CONSOLE_FONT_INFOEX)
    res = GetCurrentConsoleFontEx(stdout, False, cts.byref(font))
    if not res:
        print("{:s} error: {:d}".format(GetCurrentConsoleFontEx.__name__, GetLastError()))
        return
    # Display font information
    print("Console information for {:}".format(font))
    for field_name, _ in font._fields_:
        field_data = getattr(font, field_name)
        if field_name == "dwFontSize":
            print("    {:s}: {{X: {:d}, Y: {:d}}}".format(field_name, field_data.X, field_data.Y))
        else:
            print("    {:s}: {:}".format(field_name, field_data))
    while 1:
        try:
            height = int(input("nEnter font height (invalid to exit): "))
        except:
            break
        # Alter font height
        font.dwFontSize.X = 10  # Changing X has no effect (at least on my machine)
        font.dwFontSize.Y = height
        # Display font information
        res = SetCurrentConsoleFontEx(stdout, False, cts.byref(font))
        if not res:
            print("{:s} error: {:d}".format(SetCurrentConsoleFontEx.__name__, GetLastError()))
            return
        print("OMG! The window changed :)")
        # Get current font characteristics again
        res = GetCurrentConsoleFontEx(stdout, False, cts.byref(font))
        if not res:
            print("{:s} error: {:d}".format(GetCurrentConsoleFontEx.__name__, GetLastError()))
            return
        print("nNew sizes    X: {:d}, Y: {:d}".format(font.dwFontSize.X, font.dwFontSize.Y))


if __name__ == "__main__":
    print("Python {:s} {:03d}bit on {:s}n".format(" ".join(elem.strip() for elem in sys.version.split("n")),
                                                   64 if sys.maxsize > 0x100000000 else 32, sys.platform))
    rc = main(*sys.argv[1:])
    print("nDone.n")
    sys.exit(rc)

Notes:

• CTypes allows low level access similar to C (only the syntax is Python)

• Code uses [MS.Learn]: SetConsoleTextAttribute function

  • In order to avoid setting invalid values, it’s used in conjunction with its counterpart: [MS.Learn]: GetCurrentConsoleFontEx function. Call that function in order to populate the CONSOLE_FONT_INFOEX structure, then modify only the desired values

  • There are "simpler" functions (e.g. [MS.Learn]: GetCurrentConsoleFont function or [MS.Learn]: GetConsoleFontSize function), but unfortunately there are no corresponding setters

  • Note that all referenced WinAPI functions are deprecated

• The ctypes.wintypes constants (which reference the standard CTypes types) are used (to give the code a Win like flavor)

• It is very (almost painfully) long (also because I’ve added proper error handling)

• An alternative, as suggested in one of the answers of [SO]: Change console font in Windows (where you copied the code from), would be to install a 3^rd-party module (e.g. [GitHub]: mhammond/pywin32 – Python for Windows (pywin32) Extensions which is a Python wrapper over WINAPIs) which would require less code to write because the bridging between Python and C would be already implemented, and probably the above functionality could be accomplished in just a few lines

• As I commented in the code, setting COORD.X seems to be ignored. But it’s automatically set when setting COORD.Y (to a value close to COORD.Y // 2 – probably to preserve the aspect ratio). On my machine (Win 10 pc064) with the currently selected font, the default value is 16. You might want to set it back at the end, to avoid leaving the console in a "challenged" state (apparently, Win adjusts Cmd window size, to be (sort of) in sync with the font size):