Modules¶

http://openbookproject.net/thinkcs/python/english3e/modules.html

module is a file containing Python definitions and statements intended for use in other Python programs
many Python modules come with built-in standard library

Various ways to import names into the current namespace¶

In [ ]:

# import math module into the global namespace
import math
x = math.sqrt(100)
print(x)

In [ ]:

import random
print(random.choice(list(range(1, 21))))

In [ ]:

from random import choice

In [ ]:

print(choice([1, 2, 3, 4]))

In [ ]:

help(math)

In [ ]:

from math import * # Import all the identifiers from math
print(sqrt(100))
print(pi)

In [ ]:

from math import radians, sin
rad = radians(90)
print(rad)
print(sin(rad))

names can be imported to local namespace¶

In [ ]:

def isUpper(letter):
    import string # string name is local
    return letter in string.ascii_uppercase

In [15]:

print(isUpper('a'))

False

In [2]:

# can we use string module outside isUpper function?
print(string.digits)

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-2-1f51304bf154> in <module>()
      1 # can we use string module outside isUpper function?
----> 2 print(string.digits)

NameError: name 'string' is not defined

scope and lookup rules¶

The scope of an identifier is the region of program code in which the identifier can be accessed, or used.

Three important scopes in Python: - Local scope refers to identifiers declared within a function - Global scope refers to all the identifiers declared within the current module, or file - Built-in scope refers to all the identifiers built into Python -- those like range and min that are (almost) always available

Precedence rule:

innermost or local scope
global scope
built-in scope

In [1]:

def testLocalScope():
    k = 5
    for i in range(2):
        for j in range(2):
            if i == j:
                k = 3
                print('inside=',k)
    print('outside=',k)

In [20]:

test()

inside= 3
inside= 3
outside= 3

In [21]:

print(k)

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-21-eb2fa875d160> in <module>()
----> 1 print(k)

NameError: name 'k' is not defined

User-defined modules¶

use module1.py, module2.py inside modules folder to demonstrate user defined modules and importance of:¶

if
        ...

Packages¶

folder with module(s)
must define __init__.py empty module to initialize as package
can't import package itself (in a useful way) but only module(s) or identifiers in the modules
https://docs.python.org/3/tutorial/modules.html#packages

use fibos package to demostrate user-defined package¶

In [3]:

import fibos

In [4]:

help(fibos)

Help on package fibos:

NAME
    fibos

PACKAGE CONTENTS
    fibo

FILE
    /Volumes/Storage/CMU/Sp2019/CS0/thinkpythonnotebooks/fibos/__init__.py

In [5]:

fibos.fibo.fib(10)

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-5-94afb397843e> in <module>()
----> 1 fibos.fibo.fib(10)

AttributeError: module 'fibos' has no attribute 'fibo'

In [6]:

import fibos.fibo as f
f.fib(10)

0 1 1 2 3 5 8 13 21 34

In [7]:

from fibos import fibo
fibo.fib(10)

0 1 1 2 3 5 8 13 21 34

In [ ]: