Why is print() not working anymore with python?

Question

in fact this should not be a problem because it\'s fairly basic. I just want to print out an array of categories, but in one line and separated by comma.

for ent         


        

Answer 1

Printing to the terminal in Python 3 is usually "line buffered". That is, the whole line is only printed to the terminal once a newline character is encountered.

To resolve this problem you should either print a new line at the end of the for loop, or flush stdout.

eg.

for entry in categories:
    print(entry, ", ", end='')
print(end='', flush=True) # or just print() if you're not fussed about a newline

However, there are better ways of printing an array out. eg.

print(", ".join(str(entry) for entry in categories))
# or
print(*categories, sep=", ")

Answer 2

You are almost certainly experiencing output buffering by line. The output buffer is flushed every time you complete a line, but by suppressing the newline you never fill the buffer far enough to force a flush.

You can force a flush using flush=True (Python 3.3 and up) or by calling the flush() method on sys.stdout:

for entry in categories:
    print(entry, ", ", end='', flush=True)

You could simplify that a little, make , the end value:

for entry in categories:
    print(entry, end=', ', flush=True)

to eliminate the space between the entry and the comma.

Alternatively, print the categories as one string by using the comma as the sep separator argument:

print(*categories, sep=', ')

Answer 3

Check categories isn't empty - that'd make it print nothing - also I'd consider changing your code to make use of the sep argument instead (depending how large categories is):

print(*categories, sep=', ')

eg:

>>> categories = range(10)
>>> print(*categories, sep=', ')
0, 1, 2, 3, 4, 5, 6, 7, 8, 9

Then you don't have to worry about flushing/trailing separators etc...