Byte frequency of text or binary file

#python 3.5
# cf1 - 1st order character distribution
# text or binary files

#set up array
from array import array
a = array("H")

# ASCII
def printable(n):
    if((n>31 and n<127)):
        return(True)
    else:
        return(False)

input_file = input("file name: ")

f = open(input_file, 'rb')

# creat and initialize array
a = [0 for i in range(256)]

while True:
    nextch = f.read(1)
    if(not nextch): break

    a[ord(nextch)] += 1

for i in range(256):
    if(a[i] > 0):
        if(printable(i)):
            print("'" + chr(i) + "'", "\t", a[i])
        else:
            print(i, "\t", a[i])

f.close()