Table of Contents

• PythonTricks
  • Useful codes
    • logger
  • Cannot load module
  • Python change font size
  • Python add xlabel
  • Python change xtick rotation
  • Numpy tricks
    • Remove a row with 'NaN'
    • Set seed
  • Installation
    • Autocompletion in the terminal
  • Command line debugger
    • Debugger
    • Profiler
    • Matlab vs Python
  • Markdown Tricks
    • TOC

PythonTricks

See also my original webpage

Useful codes

logger

Use the logger utility in your Python code to track and save your running to log file easily.

Code	Example
logger	example

We have created a Python package for the ease use of this logger - Link.

Cannot load module

If you installed a module by pip, you may cannot load it.

To be sure you install the package using the correct pip instance for your python interpreter you need to run something like:

/bin/env python -m pip install --upgrade mymodule

or for OSX

/usr/bin/env python -m pip install --upgrade mymodule

source in stack overflow

Python change font size

try the following ones

plt.rc('xtick', labelsize=15)
plt.rc('ytick', labelsize=15)
plt.tick_params(axis='both', which='major', labelsize=15)
cbar = plt.colorbar(im, cax=cax)
cbar.ax.tick_params(axis='both', which='major', labelsize=15)
plt.rcParams.update({'font.size': 15})

Python add xlabel

try the following two ways

plt.xlabel('a', fontsize=15)
plt.ylabel('b', fontsize=15)

or

ax = plt.subplot(111)
ax.set_xlabel('x', fontsize=15)
ax.set_ylabel('y', fontsize=15)

Python change xtick rotation

plt.xticks(rotation = 90)

Numpy tricks

Remove a row with 'NaN'

>>> a = np.array([[1,2,3], [4,5,np.nan], [7,8,9]])
array([[  1.,   2.,   3.],
       [  4.,   5.,  nan],
       [  7.,   8.,   9.]])

>>> a[~np.isnan(a).any(axis=1)]
array([[ 1.,  2.,  3.],
       [ 7.,  8.,  9.]])

Set seed

import numpy as np
import random

seed = 12345
np.random.seed(seed)
random.seed(seed)

Installation

Anaconda is a very good python package including all useful scientific computing tools. It can be downloaded from: link

run the following command:

 >bash Anaconda-2.x.x-Linux-x86[_64].sh 

Autocompletion in the terminal

In order to have autocompletion using TAB in the terminal, we have to load two commands:

import rlcompleter, readline
readline.parse_and_bind('tab:complete')

Those two lines can be automatically loaded by creating a .pythonrc in your home directory with those two files and by adding

export PYTHONSTARTUP=~/.pythonrc

to your .profile

Command line debugger

Debugger

 >python -m pdb <your_code.py> 

At start you are at the begining of your code. Then you can create breakpoints.

• Breakpoint at line 100 in the main file:

 (Pdb) b 100

• Breakpoint at line 50 in another file:

 (Pdb) b myclass.py:50 

You can go though your code until first breakpoint by typing 'c' (continue)

You can go though your code step by step:

• n: execute current statement
• s: execute and step into

Enable/Disable/Clear breakpoint:

• disable number
• enable number
• clear number

 (Pdb) b myclass.py:50 

• Breaking on error:

 >python -Werror -mpdb <your_code> 

Profiler

 >python -m cProfile <your_code.py> 

Matlab vs Python

Matlab	Python/Numpy
X[1] (indexing starts at 1)	X[0] (indexing starts at 0)

Markdown Tricks

TOC

Automatically generate table of content: generated with DocToc