Python

# marks dir as package. allows imports from any cwd
__init__.py

# returns names in current scope
dir()

# get help on class `sring`
help("string")

# convert to integer
int(somestring)

# change current dir
os.chdir('C\\Users')

# get current working directory
os.getcwd

# checks if file 1.c exists in directory d in the current dir
os.path.isfile("d/1.c")

# show HOME environment variable
print os.environ['HOME']

# produce a list from and including x to an including y-1
range(x, y)

# pause execution for x seconds
time.sleep(x)

# Show variable type
type(myvar)

# class of x returned as string
x.__class__.__name__

# print a list of all available modules
help('modules')

# using pip CLI tool. shows user installed packages
pip freeze

# a file containing Python definitions and statements, with the .py extension
module

# a directory of python module(s); can have nested structure with sub-packages
package

PACKAGES AND MODULES
Any Python file is a module, its name being the file's base name without the .py extension. A package is a collection of Python modules: while a module is a single Python file, a package is a directory of Python modules containing an additional __init__.py file, to distinguish a package from a directory that just happens to contain a bunch of Python scripts. Packages can be nested at any deep, providing that the corresponding directories contain their own __init__.py file.