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Code samples from the "Python Cookbook, 3rd Edition", published by O'Reilly & Associates, May, 2013.

Python 92.38% Shell 0.07% Makefile 0.09% C 7.47%

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python-cookbook's Issues

License missing

The code is not provided with any kind of license, making it difficult to determine if these snippets can be used in a professional context.

typo in section 1.2 user_record

i finally got this working by defining 'record' instead of user_record.

Just wanted to share .. thanks!

on-input-37-fd835976edf3> in ()
----> 1 user_record = name, email, *phone_numbers

NameError: name 'email' is not defined

In [38]: phone_numbers

NameError Traceback (most recent call last)
in ()
----> 1 phone_numbers

NameError: name 'phone_numbers' is not defined

#here where i set to record instead of user_record
In [39]: name, email, *phone_numbers = record

In [40]: name
Out[40]: 'Dave'

In [41]: email
Out[41]: '[email protected]'

In [42]: phone_numbers
Out[42]: ['773-555-1212', '555-555-5555']

In [43]:

Communicating between threads example

Hi!

In the Chapter 12: communicating between threads "Solution" section (bottom of p493) there is an example in which the Queue.task_done method is used along with Queue.join to wait for all items produced by the "producer" function to be consumed.

However (and unless I am misunderstanding), because the queue has no items in it before the threads start, unless the producer function immediately puts an item (before the q.join() executes in the main thread) into the queue, the queue will immediately join. For example, if you have something like:

from queue import Queue
from threading import Thread
import time

def producer(out_q):
    time.sleep(5)
    out_q.put('hello')

def consumer(in_q):
    h = in_q.get()
    print(h + ' world!')
    in_q.task_done()

q = Queue()
t1 = Thread(target=producer, args=(q,))
t2 = Thread(target=consumer, args=(q,))

t1.start()
t2.start()

q.join()
print('q joined!')

You will see:

q joined!
hello world!

I guess the fix would be putting in an initial sentinel before starting the threads?

Love the book by the way!

example2 error on running

python-cookbook/src/8/extending_classes_with_mixins/example2.py

that's seem not a solutino for minin class which needs init method, i have checked on python 2.7, this is what i got:

C:\Python27\python.exe D:/dev/python/pyqt/workapce/pyqt/widget/test/test.py
File "D:/dev/python/pyqt/workapce/pyqt/widget/test/test.py", line 2
def init(self, *args, _restrict_key_type, **kwargs):
^
SyntaxError: invalid syntax

chapter 12.7 how_to_create_a_thread_pool example1.py Error

12/how_to_create_a_thread_pool/example1.py
As you said in book, create each Thread in new connection is a bad idea. I want create a ThreadPool to handle a TCP Socket, So I open Python CookBook and look into this demo. But it doesn't work actually.
When I use PyCharm, pool.submit(echo_client, sk, addr) actually called, but can't echo back

def echo_client(sock, client_addr):
    while True:
        msg = sock.recv(65536)
        if not msg:
            break
        sock.sendall(msg)
    sock.close()

def echo_server(addr):
    pool = ThreadPoolExecutor(128)
    sock = socket(AF_INET, SOCK_STREAM)
    sock.bind(addr)
    sock.listen(5)
    while True:
        client_sock, client_addr = sock.accept()
        pool.submit(echo_client, client_sock, client_addr)  # this func called, but not truly executed to echo back
echo_server(('',15000))

My TCP client:

def tcpclient():
    skt = socket(AF_INET, SOCK_STREAM)
    skt.connect(('', 15000))
    skt.sendall('Client: To be or not, is a question'.encode())
    data = skt.recv(1024)
    print('Client recv: ', data.decode())
    skt.close()

What's Wrong with it???

python-cookbook/src/15/calling_python_from_c/embed.c cannot compiled by VC++

Hi, Dabeaz, I found it is very hard to compile with Visual Studio.
I use this command to compile:

"C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/vcvarsall.bat" amd64 && cl /W4 /EHsc /ZI /MTd /D _UNICODE /Fd:debug/ /Fo:debug/ /IC:/Python3664/include f:\py_c\embed.c /link /LIBPATH:C:/Python3664/libs /out:debug/embed.exe

I have compiled and run it successfully in MacOS with clang.

define an class to a decorator, how to understand this code, which is wraps(func)(self) without assignment

Hi,
In chapter 9.9, I don't understand the below code, especially in __init__(). It uses wraps(func)(self) in __init__(), but it doesn't assign wraps(func)(self) to self. Why self.__wrapped__ can get the original function in __call__()?

import types
from functools import wraps


class Profiled:
    def __init__(self, func):
        wraps(func)(self)
        self.ncalls = 0

    def __call__(self, *args, **kwargs):
        self.ncalls += 1
        return self.__wrapped__(*args, **kwargs)

    def __get__(self, instance, cls):
        if instance is None:
            return self
        else:
            return types.MethodType(self, instance)


@Profiled
def add(x, y):
    return x + y


print(add(1, 2))
print(add(1, 3))
print(add.ncalls)
print(add)

I changed it to self = wraps(func)(self), found that it also can work? Who can explain that? I also couldn't understand self in self = wraps(func)(self). What's "self"?

Naming a slice example

The demo of the indices method is called on a different object a than the previously instanciated one. This could be fixed ny instanciating a with the following line:

a = slice(5, 50, 2)

Cookbook

Page 48 2.7,Typo in Regex

should be re.compile(r'"(.*)"')
because with r'...', backslashes will be remained
so the findall should return [],The fix should be to delete the two backslashes.

Typo Error - 1.2. Unpacking Elements from Iterables of Arbitrary Length

In example of section 1.2 the first variable with name record must be replaced by user_record
`

user_record = ('Dave', '[email protected]', '773-555-1212', '847-555-1212')
name, email, *phone_numbers = user_record
name
'Dave'
email
'[email protected]'
phone_numbers
['773-555-1212', '847-555-1212']
`

issue of example1.py of chapter 8

hi, David

i have just tested
python-cookbook/src/8/lazily_computed_attributes/example1.py
but happened to findout it does not workout like what the book tell, which i meam python cookbook, 3rd.
After a little research, i found that you need to put a object there, like this :
class lazyproperty(object):
but i dont konw why.
please tell me if you know.

PS:

TEST based on

PyCharm 2016.3.1
Build #PY-163.9735.8, built on December 15, 2016
Subscription is active until February 25, 2017
JRE: 1.8.0_111-b14 amd64
JVM: Java HotSpot(TM) 64-Bit Server VM by Oracle Corporation

Python
2.7.11 (v2.7.11:6d1b6a68f775, Dec 5 2015, 20:40:30) [MSC v.1500 64 bit (AMD64)] on win32

what the function of "flag" in example2 how_to_determine_if_a_thread_has_started?

I don't understand the function of flag in example2 how_to_determine_if_a_thread_has_started (12.2). The scripts works fine when I remove the flag part likes below.

import threading
import time
class PeriodicTimer:
    def __init__(self, interval):
        self._interval = interval
        self._cv = threading.Condition()
    
    def start(self):
        t = threading.Thread(target=self.run)
        t.daemon = True
        t.start()
    
    def run(self):
        print('running start')
        while True:
            time.sleep(self._interval)
            with self._cv:
                self._cv.notify_all()
    
    def wait_fot_tick(self):
        with self._cv:
            self._cv.wait()


ptimer = PeriodicTimer(5)
ptimer.start()

def countdown(nticks):
    print('countdown start')
    while nticks > 0:
        ptimer.wait_fot_tick()
        print('T-minus', nticks)
        nticks -= 1


def countup(last):
    n = 0
    print('counting start')
    while n < last:
        ptimer.wait_fot_tick()
        print('Counting', n)
        n += 1


threading.Thread(target=countdown, args=(10,)).start()
threading.Thread(target=countup, args=(5,)).start()

Missing ignore_types arg when calling the method of flatten recursively

The code has missed ignore_types arg when calling the method of flatten recursively in the example about how to flatten a nested sequence.

src/4/how_to_flatten_a_nested_sequence/example.py

from collections import Iterable

def flatten(items, ignore_types=(str, bytes)):
    for x in items:
        if isinstance(x, Iterable) and not isinstance(x, ignore_types):
            yield from flatten(x)
        else:
            yield x

The corrected code is yield from flatten(x, ignore_types).

stderr='/tmp/dameon.log')