Is there a way to know if a font is Truetype or OpenType?

[moi15moi]

Is there a way to know if a font is Truetype or OpenType via fonttools?

[justvanrossum]

from fontTools.ttLib import TTFont

f = TTFont("path/to/font")
if "glyf" in f:
    print("font is TTF")
else:
    print("font is OTF")

[kenmcd]

That font is an OpenType file format with TrueType character/glyph outlines.
It comes back as TTF true based on the test above, because those TrueType glyphs are in the glyf table inside the font.
Usually this type of font has a .ttf file extension, but that is not mandatory (but is recommended).
If the font has PostScript outlines, not TrueType outlines, the glyphs are in the cff table.
So in that case the above test for the existence of the glyf table would be false.

What exactly are you trying to determine?
If a font has TrueType outlines vs. PostScript outlines?
Meaning an OpenType-TT (.ttf) font vs. an OpenType-PS (.otf usually).
OR
Are you really trying to determine if the font is the old TrueType file format vs. the newer OpenType file format?

EDIT: You posted while I was writing.
That StackOverflow test is to determine the file format as I mentioned above.

[jenskutilek]

Depending on your system, searching for font files may include a large number of TrueType collection files, which start with the tag "ttcf" and may contain either TrueType or CFF-based fonts. Your check doesn't include this case respectively counts them as "not TrueType".

[justvanrossum]

Your code is buggy: you read four bytes, but then do startswith with a five-byte string. That will always return False.

(The stackoverflow code is dodgy: while it does read 5 bytes, I don't know whether the fifth byte will always be zero. It should read four bytes.)

[justvanrossum]

Then there are Apple TrueType fonts where the first four bytes are b"true", not b"\x00\x01\x00\x00"

[moi15moi]

@justvanrossum @jenskutilek You are both totally right. I just make an wrong test

from matplotlib import font_manager
from fontTools import ttLib

fontsPath = font_manager.findSystemFonts()
numberOfDifference = 0

for path in fontsPath:
    with open(path, 'rb') as fontFile:
        fontType = fontFile.read(5)
    
    if not fontType.startswith(b'ttcf'):

        ttLibFont = ttLib.TTFont(path, fontNumber=0)

        isTrueTypeStackOverflow = False
        if fontType.startswith(b'\x00\x01\x00\x00\x00'):
            isTrueTypeStackOverflow = True
        
        isTrueTypeFonttools = False
        if "glyf" in ttLibFont:
            isTrueTypeFonttools = True

        if isTrueTypeFonttools != isTrueTypeStackOverflow:
            numberOfDifference += 1
            print(path)

print("Font: " + str(len(fontsPath)))
print("numberOfDifference: " + str(numberOfDifference))

Output

Font: 1048
numberOfDifference: 0

So, in brief, everything is good. I did not know that an .otf file is not necessary an opentype font.

My ignorance led me to think looking at the glyphs wasn't a good way to go, but I was wrong.

At least, it confimed that it is a good technic to know if it is an truetype font or an opentype font