why math.ceil return a integer in flask shell command?

Question

ENV:

python: 2.7.5
flask = 0.12.2
flask-cors = 2.0.1
flask-script = 2.0.5

start a python shell:

$ python
Python 2.7.5 (default, Nov  6 2016, 00:28:07)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import math
>>> math.ceil(3.2)
4.0

the math.ceil return a float, but when I use flask-script Shell command to start a python shell, it return an integer:

$ ./bin/python manage.py shell
==========================================
Starting server at 2018-01-06 15:30:14
==========================================

In [1]: import math

In [2]: math.ceil(3.2)
Out[2]: 4

I know math.ceil of python3 will return a integer, but i used python2, anyone has good idea?

check python version:

In [1]: import sys

In [2]: print (sys.version)
2.7.5 (default, Nov  6 2016, 00:28:07)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)]

`./bin/python` starts Python3's shell or Python2.7's ? Please check — Moinuddin Quadri, Jan 06 '18 at 07:36

score 0 · Answer 1 · answered Jan 07 '18 at 23:04

Although it looks like 4 is an integer. It is possible that flask-script is printing it without the decimal expansion. try running

math.ceil(3.2)/3

in flask-script. If it is working properly it will print 1.3333333333333333. If it prints 1 then you should try reinstalling flask-script.

score 0 · Accepted Answer · answered Jan 08 '18 at 09:24

I found the root cause, for our flask app, we add the future package.

future is the missing compatibility layer between Python 2 and Python 3. It allows you to use a single, clean Python 3.x-compatible codebase to support both Python 2 and Python 3 with minimal overhead.

This package rewrite the math.ceil method, it return an integer:

In [5]: math.ceil.func_code
Out[5]: <code object ceil at 0x7fd74853cab0, file "/data/apps/ecoboost/eggs/future-0.16.0-py2.7.egg/future/backports/misc.py", line 31>

the source code as below:

def ceil(x):
    """
    Return the ceiling of x as an int.
    This is the smallest integral value >= x.
    """
    return int(oldceil(x))

why math.ceil return a integer in flask shell command?

2 Answers2