Technology/Python/Learn
Bootstrap
Pip
Pip is an excellent tool for installing new Python packages.
$ wget https://bootstrap.pypa.io/get-pip.py
$ python get-pip.py
$ pip install xxx # or
$ python -m pip install xxx
Ignore installed:
$ pip install --ignore-installed <package>
virtualenv
virtualenv is a tool to create isolated Python environment.
Install via pip:
$ pip install virtualenv
Create a virtual environment:
$ cd /path/to/virtualenvs
$ virtualenv my_env
virtualenvwrapper
virtualenvwrapper provides a set of commands beyond virtualenv.
Install via pip:
$ pip install virtualenvwrapper
$ export WORKON_HOME=~/.virtualenvs
$ source /path/to/virtualenvwrapper.sh
Create a virtual environment:
$ cd /path/to/virtualenvs
$ mkvirtualenv my_env
Work on a virtual envonment:
$ workon my_env
Strings
Format
Input and Output
Print to stderr
- Python2
import sys
print >> sys.stderr, 'print >> sys.stderr'
sys.stderr.write('sys.stderr.write\n')
- Python3
from __future__ import print_function
import sys
print('print(, file=sys.stderr)', file=sys.stderr)
Functions
def f(x):
return x**2
g = lambda x: x**2
h = lambda: g(8)
Modules
Import Dynamically
import imp
mod = imp.load_source("bar","./foo/bar.py")
Paths
Get Script’s Path
import os
print(os.path.realpath(__file__))
print(os.path.dirname(os.path.realpath(__file__)))
Add Path to sys.path
import sys
sys.path.append(path)
sys.path.insert(0, path)
Headers
Python Interpreter
#!/usr/bin/env python
Encoding
# -*- coding: utf-8 -*-
Arguments
argparse
import argparse
def main(args):
print(args.file)
if __name__ == '__main__':
parser = argparse.ArgumentParser()
parser.add_argument('src', help='Source file')
args = parser.parse_args()
for arg in vars(args):
print('{}: {}'.format(arg, getattr(args, arg)))
main(args)