Starting Python Page 15

Page 15 of Article: Starting Python

The idea of this thread is to help the beginning Python programmer with hints and helpful code. Please feel free to contribute! If you have any questions start your own thread! The creators of Python are very active, improving the language all the time. Here is a little of the…

2 Years Ago

Show Comments

5

Questions about threading come up many times on the forum, so here some help ...

# running a function in the background with threading
# apply threading to a function with a function decorator
# without the threading decorator the function counter2
# would tick off first, then the other prints would show

import time
import threading

def background(f):
    """
    a threading decorator
    use @background above the function you want to thread
    (run in the background)
    """
    def bg_f(*a, **kw):
        threading.Thread(target=f, args=a, kwargs=kw).start()
    return bg_f

@background
def counter2(n):
    """show the count every second"""
    for k in range(n):
        print("counting %d" % k)
        time.sleep(1)

# start the counter
counter2(7)
time.sleep(0.9)
print('hello')   # prints hello, before counter prints 1
time.sleep(3)
print('world')   # prints world, before counter prints 4

''' result ...
counting 0
hello
counting 1
counting 2
counting 3
world
counting 4
counting 5
counting 6
'''

vegaseat

DaniWeb's Hypocrite

Moderator

6,499 posts since Oct 2004

Reputation Points: 1,451

Solved Threads: 1,618

Skill Endorsements: 37

2 Years Ago

0

Thanks a Lot for sharing

maninaction

Junior Poster in Training

76 posts since Jun 2011

Reputation Points: 1

Solved Threads: 7

Skill Endorsements: 0

2 Years Ago

1

Easy to overlook, random.choice() is usually used to pick an item from a list. However, it does apply to any sequence ...

import random

# pick a random letter out of a string
print(random.choice('abcdefg'))

vegaseat

DaniWeb's Hypocrite

Moderator

6,499 posts since Oct 2004

Reputation Points: 1,451

Solved Threads: 1,618

Skill Endorsements: 37

2 Years Ago

2

A simple way to display a list of lists/tuples as a table in your browser ...

# make_html_table.py
# create an html table from a data list

def make_html_table(mylist):
    """
    use a list of data tuples and create the html code
    of a html formatted table containing the data items
    """
    rows = ['<td>'+'</td><td>'.join(xx)+'</td>'+'\n' for xx in mylist]
    table = '<table border=2><tr>'
    table += '<tr>'.join(rows)
    table += '</tr></table>'
    return table

# a list of (name, age, weight) tuples (or lists)
# the first tuple is the header
data_list = [
('Name', 'Age', 'Weight'),
('Sarah Gellar', '26', '121'),
('Alec Baldwin', '47', '214'),
('Mandy Moore', '22', '135'),
('Matthew Goode', '29', '167'),
('Amanda Bynes', '19', '112'),
('James Kirk', '24', '175')
]

html_table = make_html_table(data_list)

print(html_table)  # test

# save as html file and show in your browser
with open('html_table.htm', 'w') as fout:
    fout.write(html_table)

You can use this simple code to show the above html file in your web browser ...

# use Python's webbrowser module to show an html code file 

import webbrowser

# open your web browser to run the html file
webbrowser.open('html_table.htm')

vegaseat

DaniWeb's Hypocrite

Moderator

6,499 posts since Oct 2004

Reputation Points: 1,451

Solved Threads: 1,618

Skill Endorsements: 37

2 Years Ago

Show Comments

2

The named tuple is a versatile container similar to a tuple but with named indexes replacing the numeric ones ...

# named tuples have named indexes that behave similar to class 
# instances but require no more memory than regular tuples
# tested with Python27 and Python32  by  vegaseat

import collections as co
import pprint

def create_nt_dict(data_list, Person):
    """
    load the named tuple with the data list and
    create a dictionary of the named tuple
    where the instance name is the key
    """
    nt_dict = {}
    for name, age, weight in data_list:
        # use lower first name + initial letter of last name
        # as key to avoid name collisions
        first, last = name.split()
        instance_name = first.lower() + last[0] 
        nt_dict[instance_name] = Person(name, age, weight)       
    return nt_dict   

# a test list of (name, age, weight) tuples
data_list = [
('Sarah Gellar', 26, 121),
('Alec Baldwin', 47, 214),
('Mandy Moore', 22, 135),
('Matthew Goode', 29, 167),
('Amanda Bynes', 19, 112),
('James Kirk', 24, 175)
]

# create the named tuple
# does behave like a Python class so use name 'Person'
Person = co.namedtuple('movie_star', 'name, age, weight')

# load the named tuple and get a dictionary of instances
nt_dict = create_nt_dict(data_list, Person)
# add nt_dict to dictionary local to __main__
locals().update(nt_dict)

# test_prints only ...
pprint.pprint(nt_dict)
print('<>'*35)
pprint.pprint(locals())
print('<>'*35)

# work with the named tuple ...
print("names of instances =\n%s" % sorted(nt_dict.keys()))

'''
names of instances =
['alecB', 'amandaB', 'jamesK', 'mandyM', 'matthewG', 'sarahG']
'''

# pick one instance ...
print(mandyM.name)   # Mandy Moore
print(mandyM.age)    # 22

print('<>'*35)

print("Movie stars under 25 years of age:")
for star in nt_dict:
    star = eval(star)
    if star.age < 25:
        print(star.name, star.age, star.weight)

''' Python32 result ...
Movie stars under 25 years of age:
James Kirk 24 175
Mandy Moore 22 135
Amanda Bynes 19 112
'''

vegaseat

DaniWeb's Hypocrite

Moderator

6,499 posts since Oct 2004

Reputation Points: 1,451

Solved Threads: 1,618

Skill Endorsements: 37