CODEWITHSUNDEEP
pythonstringascii
Electrons_Ahoy
Electrons_Ahoy

Reputation: 38573

How do I convert a list of ascii values to a string in python?

I've got a list in a Python program that contains a series of numbers, which are themselves ASCII values. How do I convert this into a "regular" string that I can echo to the screen?

Upvotes: 94

Views: 230176

Answers (9)

user13528444
user13528444

Reputation: 76

I've timed the existing answers. Code to reproduce is below. TLDR is that bytes(seq).decode() is by far the fastest. Results here:

 test_bytes_decode : 12.8046 μs/rep
     test_join_map : 62.1697 μs/rep
test_array_library : 63.7088 μs/rep
    test_join_list : 112.021 μs/rep
test_join_iterator : 171.331 μs/rep
    test_naive_add : 286.632 μs/rep

Setup was CPython 3.8.2 (32-bit), Windows 10, i7-2600 3.4GHz

Interesting observations:

  • The "official" fastest answer (as reposted by Toni Ruža) is now out of date for Python 3, but once fixed is still basically tied for second place
  • Joining a mapped sequence is almost twice as fast as a list comprehension
  • The list comprehension is faster than its non-list counterpart

Code to reproduce is here:

import array, string, timeit, random
from collections import namedtuple

# Thomas Wouters (https://stackoverflow.com/a/180615/13528444)
def test_join_iterator(seq):
    return ''.join(chr(c) for c in seq)

# community wiki (https://stackoverflow.com/a/181057/13528444)
def test_join_map(seq):
    return ''.join(map(chr, seq))

# Thomas Vander Stichele (https://stackoverflow.com/a/180617/13528444)
def test_join_list(seq):
    return ''.join([chr(c) for c in seq])

# Toni Ruža (https://stackoverflow.com/a/184708/13528444)
# Also from https://www.python.org/doc/essays/list2str/
def test_array_library(seq):
    return array.array('b', seq).tobytes().decode()  # Updated from tostring() for Python 3

# David White (https://stackoverflow.com/a/34246694/13528444)
def test_naive_add(seq):
    output = ''
    for c in seq:
        output += chr(c)
    return output

# Timo Herngreen (https://stackoverflow.com/a/55509509/13528444)
def test_bytes_decode(seq):
    return bytes(seq).decode()

RESULT = ''.join(random.choices(string.printable, None, k=1000))
INT_SEQ = [ord(c) for c in RESULT]
REPS=10000

if __name__ == '__main__':
    tests = {
        name: test
        for (name, test) in globals().items()
        if name.startswith('test_')
    }

    Result = namedtuple('Result', ['name', 'passed', 'time', 'reps'])
    results = [
        Result(
            name=name,
            passed=test(INT_SEQ) == RESULT,
            time=timeit.Timer(
                stmt=f'{name}(INT_SEQ)',
                setup=f'from __main__ import INT_SEQ, {name}'
                ).timeit(REPS) / REPS,
            reps=REPS)
        for name, test in tests.items()
    ]
    results.sort(key=lambda r: r.time if r.passed else float('inf'))

    def seconds_per_rep(secs):
        (unit, amount) = (
            ('s', secs) if secs > 1
            else ('ms', secs * 10 ** 3) if secs > (10 ** -3)
            else ('μs', secs * 10 ** 6) if secs > (10 ** -6)
            else ('ns', secs * 10 ** 9))
        return f'{amount:.6} {unit}/rep'

    max_name_length = max(len(name) for name in tests)
    for r in results:
        print(
            r.name.rjust(max_name_length),
            ':',
            'failed' if not r.passed else seconds_per_rep(r.time))

Upvotes: 3

ptsivakumar
ptsivakumar

Reputation: 437

def working_ascii():
    """
        G    r   e    e    t    i     n   g    s    !
        71, 114, 101, 101, 116, 105, 110, 103, 115, 33
    """

    hello = [71, 114, 101, 101, 116, 105, 110, 103, 115, 33]
    pmsg = ''.join(chr(i) for i in hello)
    print(pmsg)

    for i in range(33, 256):
        print(" ascii: {0} char: {1}".format(i, chr(i)))

working_ascii()

Upvotes: 3

Timo Herngreen
Timo Herngreen

Reputation: 132

You can use bytes(list).decode() to do this - and list(string.encode()) to get the values back.

Upvotes: 10

Idan Rakovsky
Idan Rakovsky

Reputation: 11

Question = [67, 121, 98, 101, 114, 71, 105, 114, 108, 122]
print(''.join(chr(number) for number in Question))

Upvotes: 0

David White
David White

Reputation: 113

Perhaps not as Pyhtonic a solution, but easier to read for noobs like me:

charlist = [34, 38, 49, 67, 89, 45, 103, 105, 119, 125]
mystring = ""
for char in charlist:
    mystring = mystring + chr(char)
print mystring

Upvotes: 6

Toni Ruža
Toni Ruža

Reputation: 7512

import array
def f7(list):
    return array.array('B', list).tostring()

from Python Patterns - An Optimization Anecdote

Upvotes: 14

Reputation:

Same basic solution as others, but I personally prefer to use map instead of the list comprehension:


>>> L = [104, 101, 108, 108, 111, 44, 32, 119, 111, 114, 108, 100]
>>> ''.join(map(chr,L))
'hello, world'

Upvotes: 28

Thomas Vander Stichele
Thomas Vander Stichele

Reputation: 36529

l = [83, 84, 65, 67, 75]

s = "".join([chr(c) for c in l])

print s

Upvotes: 8

Thomas Wouters
Thomas Wouters

Reputation: 133405

You are probably looking for 'chr()':

>>> L = [104, 101, 108, 108, 111, 44, 32, 119, 111, 114, 108, 100]
>>> ''.join(chr(i) for i in L)
'hello, world'

Upvotes: 166

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