I am trying to access the value of pi in Python 2.7, but it seems as if Python doesn't recognize math.pi. I am using IDLE, and when I try to print the value of math.pi, it says that "Math is not defined" or "math is not defined". I can't upgrade to the next version without risk, so is there a way to access pi in Python 2.7? Alternatively, is there another way to convert degrees to radians in Python 2.7 without dealing with Pi?
Python 2.7.5 (default, May 15 2013, 22:44:16) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import math
>>> math.pi
3.141592653589793
Check out the Python tutorial on modules and how to use them.
As for the second part of your question, Python comes with batteries included, of course:
>>> math.radians(90)
1.5707963267948966
>>> math.radians(180)
3.141592653589793
To have access to stuff provided by math module, like pi. You need to import the module first:
import math
print (math.pi)
Related
In Python 2.7, how can I make the IDLE app use \__future__ division without typing from \__future__ import division manually every time I start IDLE?
If I put from \__future__ import division at the top of my .idlestartup file it is ignored, even though the other things in .idlestartup get executed. For example:
~> cat >.idlestartup
from __future__ import division
print("Executing .idlestartup")
~> idle -s
Here's what my IDLE window looks like after I try dividing:
Python 2.7.8 |Anaconda 2.1.0 (x86_64)| (default, Aug 21 2014, 15:21:46)
[GCC 4.2.1 (Apple Inc. build 5577)] on darwin
Type "copyright", "credits" or "license()" for more information.
>>>
Executing .idlestartup
>>> 2/3
0
>>>
I am using Mac OS X 10.9.5 Mavericks (also had the same problem on earlier versions of OS X). Note that the command line version above was included to make it easier to show what I'm talking about, but the version I'm more interested in is running the IDLE app from the GUI.
The solution suggested by Ashwini Chaudhary below worked for running the Anaconda version from the command line but not for running the IDLE app.
I was finally able to get future division working automatically in the IDLE app by adding "sys.argv.insert(1, '-Qnew')" to /Applications/IDLE.app/Contents/MacOS/IDLE. Both that and Ashwini Chaudhary's solution below seem brittle. I wonder if there is a cleaner way.
Adding the __future__ statement at the top of /usr/lib/python2.7/idlelib/PyShell.py did the job for me.
I am on Ubuntu, the path may vary for other OS:
>>> import idlelib
>>> idlelib.PyShell.__file__
'/usr/lib/python2.7/idlelib/PyShell.py'
I'm new to python, and I'm trying to get a basic working understanding of changing the working directory and working with .py files. At the moment, I've changed the directory to where a couple of my .py files are, but when I go to import them, I get a time lag of over a minute for each one. Is that to be expected? Any idea what's going on? Here's what I'm doing:
Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:06:53) [MSC v.1600 64 bit (AMD64)] on win32
Type "copyright", "credits" or "license()" for more information.
>>> import os
>>> os.getcwd()
'C:\\Python33'
>>> os.chdir("C:/Users/MarketResearch")
>>> import EarningsDownload
>>> import RatingsChanges
>>>
Sounds like your module is actually doing work when it is imported. This is (usually) a bad idea. What you should do instead is put your setup code into a function, say setup() or initialize(), and then call it after importing:
import earnings_download
earnings_download.initialize()
In python 2.7, by using
from __future__ import division, print_function
I can now have print(1/2) showing 0.5.
However is it possible to have this automatically imported at python startup ?
I tried to use the sitecustomize.py special module but the inport is only valid inside the module and not in the shell.
As I'm sure people will ask why I need that : teaching Python to teenagers I noticed that the integer division was not easy for them so we decided to switch to Python 3. However one of the requirement of the course was to be able to plot function and Matplotlib is pretty good but only valid for Python 2.7.
So my idea was to use a custom 2.7 installation...not perfect but I don't have a better idea to have both Matplotlib and the new "natural" division "1/2=0.5".
Any advice or maybe a Matplotlib alternative that is working on python 3.2 ?
matplotlib on python 3 is closer than you may think: https://github.com/matplotlib/matplotlib-py3; http://www.lfd.uci.edu/~gohlke/pythonlibs/#matplotlib.
Why not use PYTHONSTARTUP instead of sitecustomize.py?
localhost-2:~ $ cat startup.py
from __future__ import print_function
from __future__ import division
localhost-2:~ $ export PYTHONSTARTUP=""
localhost-2:~ $ python
Python 2.7.2 (v2.7.2:8527427914a2, Jun 11 2011, 15:22:34)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 1/2
0
>>> print("fred",end=",")
File "<stdin>", line 1
print("fred",end=",")
^
SyntaxError: invalid syntax
>>> ^D
localhost-2:~ $ export PYTHONSTARTUP=startup.py
localhost-2:~ $ python
Python 2.7.2 (v2.7.2:8527427914a2, Jun 11 2011, 15:22:34)
[GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> 1/2
0.5
>>> print("fred",end=",")
fred,>>>
No need to compile a new version of Python 2.x. You can do this at start up.
As you found, sitecustomize.py does not work. This is because the from __future__ import IDENTIFIER isn't an import. It flags the module to be compiled under special rules. Any module that uses those features must have the __future__ import, as well as the interactive console.
The following shell command will start the interactive console with division and print_function active:
python -ic "from __future__ import division, print_function"
You could alias to python (on linux) or set up a launcher to hide the extra stuff.
If you are using IDLE, the PYTHONSTARTUP script #DSM suggests should work there as well.
Note that these are not global throughout the interpreter, it only affects the interactive console. Modules on the file-system must import from __future__ explicitly to use the feature. If this is an issue, I suggest making a template to base work off of with all the needed imports:
# True division
from __future__ import division
# Modules
import matplotlib
# ... code ...
def main():
pass
if __name__ == "__main__":
main()
This may not be practical, but you may be able to compile a custom Python with the Python 3 division behavior backported. The problem with this is matplotlib might require the Python 2 behavior (although I'm not sure).
I am not getting the reason why my python script is not working though I hv put all the things correctly as my knowledge.The below test I did and it worked fine.But when I import the MySQLdb in my script it gives error as no module name MySQLdb.
**C:\Python26>python
Python 2.6.1 (r261:67517, Dec 4 2008, 16:51:00) [MSC v.1500 32 bit (Intel)] on
win32
Type "help", "copyright", "credits" or "license" for more information.
import MySQLdb
**
Kindly let me know the reason for this error.
And all the development is going on in windows XP, python 2.6, mysql 4.0.3
Earlier 1 hour back I have posted the question but some mistake was there in the question itself..
seems like the path is not set properly.
Getting two different modification time when calculated from different Python versions on Windows XP.
Python2.4
C:\Copy of elisp>c:\python24\python
Python 2.4.4 (#71, Oct 18 2006, 08:34:43) [MSC v.1310 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.path.getmtime("auto-complete-emacs-lisp.el")
1251684178
>>> ^Z
Python2.6
C:\Copy of elisp>C:\Python26\python
Python 2.6.4 (r264:75708, Oct 26 2009, 08:23:19) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.path.getmtime("auto-complete-emacs-lisp.el")
1251687778.0
>>>
There is a difference of 3600 seconds reported by Python2.6 and Python2.4.
What is the reason of this strange behavior?
It's a bug in Microsoft's implementation of the C standard library. Python 2.4 used to use the stdlib fstat call to get file information, and hence could end up an hour out in locales that use DST.
In Python 2.5 and later, os.stat calls the direct Win32-only API to get file information when running on Windows, resulting in the correct output. See this thread for more.
There is a difference of 3600 seconds ...
This should be the kicker. It's a timezone problem, pure and simple.
Now all you have to do is find out why 2.4 and 2.6 are using different timezone information :-)