How to print without a newline or space – Dev

The best answers to the question “How to print without a newline or space” in the category Dev.

QUESTION:

I’d like to do it in Python. What I’d like to do in this example in C:

#include <stdio.h>

int main() {
    int i;
    for (i=0; i<10; i++) printf(".");
    return 0;
}

Output:

..........

In Python:

>>> for i in range(10): print('.')
.
.
.
.
.
.
.
.
.
.
>>> print('.', '.', '.', '.', '.', '.', '.', '.', '.', '.')
. . . . . . . . . .

In Python, print will add a \n or space. How can I avoid that? I’d like to know how to “append” strings to stdout.

ANSWER:

For Python 2 and earlier, it should be as simple as described in Re: How does one print without a CR? by Guido van Rossum (paraphrased):

Is it possible to print something, but not automatically have a
carriage return appended to it?

Yes, append a comma after the last argument to print. For instance, this loop prints the numbers 0..9 on a line separated by spaces. Note the parameterless “print” that adds the final newline:

>>> for i in range(10):
...     print i,
... else:
...     print
...
0 1 2 3 4 5 6 7 8 9
>>>

ANSWER:

In Python 3, you can use the sep= and end= parameters of the print function:

To not add a newline to the end of the string:

print('.', end='')

To not add a space between all the function arguments you want to print:

print('a', 'b', 'c', sep='')

You can pass any string to either parameter, and you can use both parameters at the same time.

If you are having trouble with buffering, you can flush the output by adding flush=True keyword argument:

print('.', end='', flush=True)

Python 2.6 and 2.7

From Python 2.6 you can either import the print function from Python 3 using the __future__ module:

from __future__ import print_function

which allows you to use the Python 3 solution above.

However, note that the flush keyword is not available in the version of the print function imported from __future__ in Python 2; it only works in Python 3, more specifically 3.3 and later. In earlier versions you’ll still need to flush manually with a call to sys.stdout.flush(). You’ll also have to rewrite all other print statements in the file where you do this import.

Or you can use sys.stdout.write()

import sys
sys.stdout.write('.')

You may also need to call

sys.stdout.flush()

to ensure stdout is flushed immediately.

ANSWER:

Use the Python 3-style print function for Python 2.6+ (it will also break any existing keyworded print statements in the same file).

# For Python 2 to use the print() function, removing the print keyword
from __future__ import print_function
for x in xrange(10):
    print('.', end='')

To not ruin all your Python 2 print keywords, create a separate printf.py file:

# printf.py

from __future__ import print_function

def printf(str, *args):
    print(str % args, end='')

Then, use it in your file:

from printf import printf
for x in xrange(10):
    printf('.')
print 'done'
#..........done

More examples showing the printf style:

printf('hello %s', 'world')
printf('%i %f', 10, 3.14)
#hello world10 3.140000

ANSWER:

Note: The title of this question used to be something like “How to printf in Python”

Since people may come here looking for it based on the title, Python also supports printf-style substitution:

>>> strings = [ "one", "two", "three" ]
>>>
>>> for i in xrange(3):
...     print "Item %d: %s" % (i, strings[i])
...
Item 0: one
Item 1: two
Item 2: three

And, you can handily multiply string values:

>>> print "." * 10
..........