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The print statement and integer division

Two Python 2 behaviours that change results without a warning: print as a statement, and division that floors between integers.

import sys

print "hello"                  # no parentheses required
print "value:", 42             # a trailing comma means "no newline"
print "still the same line",
print                          # a bare print emits just the newline

print >>sys.stderr, "warning: writing to a file object"
print >>open("out.txt", "w"), "redirected"

print "count = " + 3           # TypeError: cannot concatenate 'str' and 'int'
print "count =", 3             # this works, because print applies str() to each item
  • The trailing comma does not separate items — it suppresses the newline and adds a space before the next output.
  • print >>f, x is the redirect syntax: any object with a write method will do, including sys.stderr.
  • Parentheses are just grouping here, so print("a", "b") prints the tuple ('a', 'b') — a two-item tuple, not two words.
  • Adding from __future__ import print_function as the first line of a file makes the identical syntax behave exactly as in Python 3.
  • A bare print is also valid inside a function, where Python 3 would need print().

Division between integers floors

print 7 / 2        # 3     int / int floors, it does not truncate
print 7.0 / 2      # 3.5   one float operand promotes the result
print -7 / 2       # -4    floors toward negative infinity, so NOT -3
print 7 % -2       # -1    the result takes the sign of the divisor
print 7 // 2       # 3     the explicit floor operator exists in Python 2 too

from __future__ import division    # must be the first statement in the file

print 7 / 2        # 3.5   true division, matching Python 3
print 7 // 2       # 3     integer division is now explicit
Expression, no future importResultWhy
7 / 23int / int is floor division
7 // 23Explicit floor division, same answer
7.0 / 23.5A float operand promotes the result
-7 / 2-4Floors downward; it does not truncate toward zero
-7 // 2-4The same flooring rule
7 % -2-1The remainder follows the sign of the divisor
10 ** 20 / 3A longIntegers promote to long automatically on overflow
float(7) / 23.5The portable way to force true division today
⚠️
This is the single most damaging porting bug in Python 2 code, because it fails silently. total / count computes an average in Python 3 and a floored quotient in Python 2, and every test written with values that divide exactly will still pass. Put from __future__ import division at the top of every legacy file you touch, then review each / and change it to // where you really did mean integer division.

FAQ

Why does print add a space between items?
Because that is what the statement does: it applies str() to each argument and joins them with a single space, then writes a newline unless the line ends with a comma. There is no way to change the separator without switching to print_function or building the string yourself.
Can I use parentheses with print to be future-proof?
Only with the future import. Without it, print("a", "b") is a tuple expression and prints ('a', 'b'); with a single argument it looks correct by accident, which is exactly why the trap survives unnoticed.

Migrating to Python 3 Python: getting started

Last refreshed 2026-09-18.