Test if a python string is printable

Question

I have some code that pulls data from a com-port and I want to make sure that what I got really is a printable string (i.e. ASCII, maybe UTF-8) before printing it. Is there a function for doing this? The first half dozon places I looked didn't have anything that looks like what I want. (string has printable but I didn't see anything (there or in the string methods) to check if every char in one string is in another.

Note: control characters are not printable for my purposes.

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Edit: I was/am looking for a single function, not a roll your own solution:

What I ended up with is:

all(ord(c) < 127 and c in string.printable for c in input_str)

Answer 1

try/except seems the best way:

def isprintable(s, codec='utf8'):
    try: s.decode(codec)
    except UnicodeDecodeError: return False
    else: return True

I would not rely on string.printable, which might deem "non-printable" control characters that can commonly be "printed" for terminal control purposes (e.g., in "colorization" ANSI escape sequences, if your terminal is ANSI-compliant). But that, of course, depends on your exact purposes for wanting to check this!-)

Answer 2

As you've said the string module has printable so it's just a case of checking if all the characters in your string are in printable:

>>> hello = 'Hello World!'
>>> bell = chr(7)
>>> import string
>>> all(c in string.printable for c in hello)
True
>>> all(c in string.printable for c in bell)
False

You could convert both strings to sets - so the set would contain each character in the string once - and check if the set created by your string is a subset of the printable characters:

>>> printset = set(string.printable)
>>> helloset = set(hello)>>> bellset = set(bell)
>>> helloset
set(['!', ' ', 'e', 'd', 'H', 'l', 'o', 'r', 'W'])
>>> helloset.issubset(printset)
True
>>> set(bell).issubset(printset)
False

So, in summary, you'd probably want to do this:

import string
printset = set(string.printable)
isprintable = set(yourstring).issubset(printset)