Put
importer.py
in the directory that holds all your other Python scripts.
For the time being,
put
date.py
there too.
Run the above file
importer.py,
which imports the module
date.
The output comes from
lines
15–36
of
importer.py.
No output comes from
lines
98–104
of
date.py
because the variable
__name__
(two underscores in front, two in back)
in
line
97
of
date.py
contains the string
"date".
The current directory is /Users/myname/python The import statement searches the following directories. 1 /Users/myname/python 2 /Users/myname/Documents 3 /Library/Frameworks/Python.framework/Versions/3.8/lib/python38.zip 4 /Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8 5 /Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/lib-dynload 6 /Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages The following module has been loaded: <module 'date' from '/Users/myname/python/date.py'> date.__file__ = /Users/myname/python/date.py d = 12/31/2019 type(d) = <class 'date.Date'>
Run the file
date.py
by itself,
without
importer.py.
You can run
date.py
from IDLE,
or in two different ways from the Terminal command line.
With the
-m
option, you can omit the
.py
filename extension, just like in an
import
statement.
(In the Microsoft Windows command prompt, say
py.exe
instead of
python3.)
python3 date.py python3 -m date pydoc3 --help pydoc3 topics pydoc3 /Users/myname/python/date.py pydoc3 ~/python/date.py pydoc3 -b Server ready at http://localhost:50240/ Server commands: [b]rowser, [q]uit server>
The output now comes from
lines
98–104
of
date.py,
because the variable
__name__
in
line
97
of
date.py
now contains the string
"__main__",
making the
if
in
line
97
true.
Today is 11/07/2019.
We saw another example of a module with a small demonstration section in tkinter Flag.
In the Python 3.8.0 Shell window of IDLE, say
>>> import date >>> help(date) Help on module date: NAME date - date.py DESCRIPTION This module is named date.py. You can import it by saying import date at the top of your Python script. CLASSES builtins.object Date class Date(builtins.object) | Class Date demonstrates class and instance attributes, class and instance methods. | It is a simple date class, containing year, month, and day integers. | | Methods defined here: | | __init__(self, month, day, year) | Initialize self. See help(type(self)) for accurate signature. | | __str__(self) | Return a string that looks like the contents of myself. | | dayOfYear(self) | Return my day of the year: a number in the range 1 to 365 inclusive. | | getDay(self) | Return the number of my day (1 to the length of my month, inclusive). | | getMonth(self) | Return the number of my month (1 to 12 inclusive). | | getYear(self) | Return my year. | | monthsInYear() | Return the number of months in a year. This function is selfless. | | nextDay(self) | Move myself one day into the future. | | nextDays(self, n) | Move myself n days into the future. | | ---------------------------------------------------------------------- | Data descriptors defined here: | | __dict__ | dictionary for instance variables (if defined) | | __weakref__ | list of weak references to the object (if defined) | | ---------------------------------------------------------------------- | Data and other attributes defined here: | | lengths = [None, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31] FILE /Users/myname/python/date.py >>>
You can do the same thing in a Terminal command line.
(In the Microsoft Windows command prompt, say
py.exe
instead of
python3.)
In
help,
press return or q.
python3 Python 3.8.0 (v3.8.0:fa919fdf25, Oct 14 2019, 10:23:27) [Clang 6.0 (clang-600.0.57)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> import date >>> help(date) Help on module date: etc. >>> help(date.Date) Help on class Date in module date: etc. >>> control-d
importer.py
uses only one thing from the module
date,
namely the class
Date.
(Actually, there are no other things in this very simple module.)
To import only that one thing,
and to get on a first-name basis with that one thing,
change
line
10
of
importer.py
from
import date #Import everything in the module date.py.
to
from date import Date #Import only the class Date from the module date.py.
and change
line
27
from
d = date.Date(12, 31, 2019) #We used to have to refer to Date by its full name.
to
d = Date(12, 31, 2019) #We are now on a first-name basis with class Date.
The last line of output remains
type(d) = <class 'date.Date'>
Date
too long to type?
If so,
change
line
10
of
importer.py
to
from date import Date as D
and change
line
27
to
d = D(12, 31, 2019)
The last line of output remains
type(d) = <class 'date.Date'>
sys.path?
A Python script run from the command line
(macOS Terminal, Linux shell, Microsoft Windows command prompt),
but not from IDLE,
will have the contents of the environment variable
PYTHONPATH
prefixed to its
sys.path.
A Python script run from IDLE does receive a
PYTHONPATH
environment variable,
but it is not added to the script’s
sys.path.
import os
if "PYTHONPATH" in os.environ: #os.environ is a dictionary. pythonpath = os.environ["PYTHONPATH"] directories = pythonpath.split(os.pathsep) #os.pathsep is a one-character string. #directories is a list of strings. for i, directory in enumerate(directories, start = 1): print(i, directory)Run from the macOS Terminal, or from my Fedora Linux,
PYTHONPATH
was empty.
Run from macOS IDLE,
PYTHONPATH
was
1 /Applications/Python 3.8/IDLE.app/Contents/Resources