Develop Reference

timedelta issue in python3.9 vs.python3.6

I have the following class in a file called 'GPS_Date.py':
import datetime
from math import floor
class GPS_Date(datetime.datetime):
ref_date = datetime.datetime(1980, 1, 6)
def __init__(self, year, month, day, hour=0, minute=0, second=0):
datetime.datetime.__init__(year, month, day, hour, minute, second)
def gps_week(self):
difftime = self-self.ref_date
return floor(difftime.days / 7)
def day_of_week(self):
difftime = self-self.ref_date
return difftime.days % 7
def day_of_year(self):
return self.timetuple().tm_yday
#staticmethod
def to_GPS_date(date):
return GPS_Date(date.year, date.month, date.day, date.hour, date.minute, date.second)
#staticmethod
def now():
return GPS_Date.to_GPS_date(datetime.datetime.utcnow())
When I run the following code in python3.6 I get the correct solution:
import datetime
from GPS_Date import GPS_Date
time_string = '2019-01-01 23:59:30.0'
date_format = '%Y-%m-%d %H:%M:%S.%f'
time_1 = datetime.datetime.strptime(time_string, date_format)
time_2 = GPS_Date.to_GPS_date(time_1)
add_time = time_2 + datetime.timedelta(minutes=30)
But when I run it with python3.9 I get the following error:
add_time = time_2 + datetime.timedelta(minutes=30)
TypeError: __init__() takes from 4 to 7 positional arguments but 9 were given
I assume something has been changed between python3.6 and python3.9. I've looked at documentation but haven't found anything. Can anyone enlighten me?

datetime.datetime does have more arguments that can be passed than GPS_Date accounts for (i.e. tzinfo and fold). Why this doesn't blow up in Python3.6, I am not sure. But you don't need to override __init__ at all, since you aren't doing anything:
class GPS_Date(datetime.datetime):
ref_date = datetime.datetime(1980, 1, 6)
def gps_week(self):
difftime = self - self.ref_date
return floor(difftime.days / 7)
def day_of_week(self):
difftime = self - self.ref_date
return difftime.days % 7
def day_of_year(self):
return self.timetuple().tm_yday
#staticmethod
def to_GPS_date(date):
return GPS_Date(date.year, date.month, date.day, date.hour, date.minute, date.second)
#staticmethod
def now():
return GPS_Date.to_GPS_date(datetime.datetime.utcnow())
is perfectly fine. (Also note: If you were to do something, you need to override __new__ instead of __init__)

Running a Python web scraper every hour [duplicate]

I'm looking for a library in Python which will provide at and cron like functionality.
I'd quite like have a pure Python solution, rather than relying on tools installed on the box; this way I run on machines with no cron.
For those unfamiliar with cron: you can schedule tasks based upon an expression like:
0 2 * * 7 /usr/bin/run-backup # run the backups at 0200 on Every Sunday
0 9-17/2 * * 1-5 /usr/bin/purge-temps # run the purge temps command, every 2 hours between 9am and 5pm on Mondays to Fridays.
The cron time expression syntax is less important, but I would like to have something with this sort of flexibility.
If there isn't something that does this for me out-the-box, any suggestions for the building blocks to make something like this would be gratefully received.
Edit
I'm not interested in launching processes, just "jobs" also written in Python - python functions. By necessity I think this would be a different thread, but not in a different process.
To this end, I'm looking for the expressivity of the cron time expression, but in Python.
Cron has been around for years, but I'm trying to be as portable as possible. I cannot rely on its presence.

If you're looking for something lightweight checkout schedule:
import schedule
import time
def job():
print("I'm working...")
schedule.every(10).minutes.do(job)
schedule.every().hour.do(job)
schedule.every().day.at("10:30").do(job)
while 1:
schedule.run_pending()
time.sleep(1)
Disclosure: I'm the author of that library.

You could just use normal Python argument passing syntax to specify your crontab. For example, suppose we define an Event class as below:
from datetime import datetime, timedelta
import time
# Some utility classes / functions first
class AllMatch(set):
"""Universal set - match everything"""
def __contains__(self, item): return True
allMatch = AllMatch()
def conv_to_set(obj): # Allow single integer to be provided
if isinstance(obj, (int,long)):
return set([obj]) # Single item
if not isinstance(obj, set):
obj = set(obj)
return obj
# The actual Event class
class Event(object):
def __init__(self, action, min=allMatch, hour=allMatch,
day=allMatch, month=allMatch, dow=allMatch,
args=(), kwargs={}):
self.mins = conv_to_set(min)
self.hours= conv_to_set(hour)
self.days = conv_to_set(day)
self.months = conv_to_set(month)
self.dow = conv_to_set(dow)
self.action = action
self.args = args
self.kwargs = kwargs
def matchtime(self, t):
"""Return True if this event should trigger at the specified datetime"""
return ((t.minute in self.mins) and
(t.hour in self.hours) and
(t.day in self.days) and
(t.month in self.months) and
(t.weekday() in self.dow))
def check(self, t):
if self.matchtime(t):
self.action(*self.args, **self.kwargs)
(Note: Not thoroughly tested)
Then your CronTab can be specified in normal python syntax as:
c = CronTab(
Event(perform_backup, 0, 2, dow=6 ),
Event(purge_temps, 0, range(9,18,2), dow=range(0,5))
)
This way you get the full power of Python's argument mechanics (mixing positional and keyword args, and can use symbolic names for names of weeks and months)
The CronTab class would be defined as simply sleeping in minute increments, and calling check() on each event. (There are probably some subtleties with daylight savings time / timezones to be wary of though). Here's a quick implementation:
class CronTab(object):
def __init__(self, *events):
self.events = events
def run(self):
t=datetime(*datetime.now().timetuple()[:5])
while 1:
for e in self.events:
e.check(t)
t += timedelta(minutes=1)
while datetime.now() < t:
time.sleep((t - datetime.now()).seconds)
A few things to note: Python's weekdays / months are zero indexed (unlike cron), and that range excludes the last element, hence syntax like "1-5" becomes range(0,5) - ie [0,1,2,3,4]. If you prefer cron syntax, parsing it shouldn't be too difficult however.

More or less same as above but concurrent using gevent :)
"""Gevent based crontab implementation"""
from datetime import datetime, timedelta
import gevent
# Some utility classes / functions first
def conv_to_set(obj):
"""Converts to set allowing single integer to be provided"""
if isinstance(obj, (int, long)):
return set([obj]) # Single item
if not isinstance(obj, set):
obj = set(obj)
return obj
class AllMatch(set):
"""Universal set - match everything"""
def __contains__(self, item):
return True
allMatch = AllMatch()
class Event(object):
"""The Actual Event Class"""
def __init__(self, action, minute=allMatch, hour=allMatch,
day=allMatch, month=allMatch, daysofweek=allMatch,
args=(), kwargs={}):
self.mins = conv_to_set(minute)
self.hours = conv_to_set(hour)
self.days = conv_to_set(day)
self.months = conv_to_set(month)
self.daysofweek = conv_to_set(daysofweek)
self.action = action
self.args = args
self.kwargs = kwargs
def matchtime(self, t1):
"""Return True if this event should trigger at the specified datetime"""
return ((t1.minute in self.mins) and
(t1.hour in self.hours) and
(t1.day in self.days) and
(t1.month in self.months) and
(t1.weekday() in self.daysofweek))
def check(self, t):
"""Check and run action if needed"""
if self.matchtime(t):
self.action(*self.args, **self.kwargs)
class CronTab(object):
"""The crontab implementation"""
def __init__(self, *events):
self.events = events
def _check(self):
"""Check all events in separate greenlets"""
t1 = datetime(*datetime.now().timetuple()[:5])
for event in self.events:
gevent.spawn(event.check, t1)
t1 += timedelta(minutes=1)
s1 = (t1 - datetime.now()).seconds + 1
print "Checking again in %s seconds" % s1
job = gevent.spawn_later(s1, self._check)
def run(self):
"""Run the cron forever"""
self._check()
while True:
gevent.sleep(60)
import os
def test_task():
"""Just an example that sends a bell and asd to all terminals"""
os.system('echo asd | wall')
cron = CronTab(
Event(test_task, 22, 1 ),
Event(test_task, 0, range(9,18,2), daysofweek=range(0,5)),
)
cron.run()

None of the listed solutions even attempt to parse a complex cron schedule string. So, here is my version, using croniter. Basic gist:
schedule = "*/5 * * * *" # Run every five minutes
nextRunTime = getNextCronRunTime(schedule)
while True:
roundedDownTime = roundDownTime()
if (roundedDownTime == nextRunTime):
####################################
### Do your periodic thing here. ###
####################################
nextRunTime = getNextCronRunTime(schedule)
elif (roundedDownTime > nextRunTime):
# We missed an execution. Error. Re initialize.
nextRunTime = getNextCronRunTime(schedule)
sleepTillTopOfNextMinute()
Helper routines:
from croniter import croniter
from datetime import datetime, timedelta
# Round time down to the top of the previous minute
def roundDownTime(dt=None, dateDelta=timedelta(minutes=1)):
roundTo = dateDelta.total_seconds()
if dt == None : dt = datetime.now()
seconds = (dt - dt.min).seconds
rounding = (seconds+roundTo/2) // roundTo * roundTo
return dt + timedelta(0,rounding-seconds,-dt.microsecond)
# Get next run time from now, based on schedule specified by cron string
def getNextCronRunTime(schedule):
return croniter(schedule, datetime.now()).get_next(datetime)
# Sleep till the top of the next minute
def sleepTillTopOfNextMinute():
t = datetime.utcnow()
sleeptime = 60 - (t.second + t.microsecond/1000000.0)
time.sleep(sleeptime)

I know there are a lot of answers, but another solution could be to go with decorators. This is an example to repeat a function everyday at a specific time. The cool think about using this way is that you only need to add the Syntactic Sugar to the function you want to schedule:
#repeatEveryDay(hour=6, minutes=30)
def sayHello(name):
print(f"Hello {name}")
sayHello("Bob") # Now this function will be invoked every day at 6.30 a.m
And the decorator will look like:
def repeatEveryDay(hour, minutes=0, seconds=0):
"""
Decorator that will run the decorated function everyday at that hour, minutes and seconds.
:param hour: 0-24
:param minutes: 0-60 (Optional)
:param seconds: 0-60 (Optional)
"""
def decoratorRepeat(func):
#functools.wraps(func)
def wrapperRepeat(*args, **kwargs):
def getLocalTime():
return datetime.datetime.fromtimestamp(time.mktime(time.localtime()))
# Get the datetime of the first function call
td = datetime.timedelta(seconds=15)
if wrapperRepeat.nextSent == None:
now = getLocalTime()
wrapperRepeat.nextSent = datetime.datetime(now.year, now.month, now.day, hour, minutes, seconds)
if wrapperRepeat.nextSent < now:
wrapperRepeat.nextSent += td
# Waiting till next day
while getLocalTime() < wrapperRepeat.nextSent:
time.sleep(1)
# Call the function
func(*args, **kwargs)
# Get the datetime of the next function call
wrapperRepeat.nextSent += td
wrapperRepeat(*args, **kwargs)
wrapperRepeat.nextSent = None
return wrapperRepeat
return decoratorRepeat

I like how the pycron package solves this problem.
import pycron
import time
while True:
if pycron.is_now('0 2 * * 0'): # True Every Sunday at 02:00
print('running backup')
time.sleep(60) # The process should take at least 60 sec
# to avoid running twice in one minute
else:
time.sleep(15) # Check again in 15 seconds

There isn't a "pure python" way to do this because some other process would have to launch python in order to run your solution. Every platform will have one or twenty different ways to launch processes and monitor their progress. On unix platforms, cron is the old standard. On Mac OS X there is also launchd, which combines cron-like launching with watchdog functionality that can keep your process alive if that's what you want. Once python is running, then you can use the sched module to schedule tasks.

Another trivial solution would be:
from aqcron import At
from time import sleep
from datetime import datetime
# Event scheduling
event_1 = At( second=5 )
event_2 = At( second=[0,20,40] )
while True:
now = datetime.now()
# Event check
if now in event_1: print "event_1"
if now in event_2: print "event_2"
sleep(1)
And the class aqcron.At is:
# aqcron.py
class At(object):
def __init__(self, year=None, month=None,
day=None, weekday=None,
hour=None, minute=None,
second=None):
loc = locals()
loc.pop("self")
self.at = dict((k, v) for k, v in loc.iteritems() if v != None)
def __contains__(self, now):
for k in self.at.keys():
try:
if not getattr(now, k) in self.at[k]: return False
except TypeError:
if self.at[k] != getattr(now, k): return False
return True

I don't know if something like that already exists. It would be easy to write your own with time, datetime and/or calendar modules, see http://docs.python.org/library/time.html
The only concern for a python solution is that your job needs to be always running and possibly be automatically "resurrected" after a reboot, something for which you do need to rely on system dependent solutions.

calling a method inside a class-Python

class Time:
def __init__(self,x,y,z):
self.hour=x
self.minute=y
self.second=z
def __str__(self):
return "({:02d}:{:02d}:{:02d})".format(self.hour, self.minute, self.second)
def time_to_int(time):
minutes=time.hour*60+time.minute
seconds=minutes*60+time.second
return seconds
def int_to_time(seconds):
time=Time()
minutes,time.second=divmod(seconds,60)
time.hour,time.minute=divmod(minutes,60)
return time
def add_time(t1,t2):
seconds=time_to_int(t1)+time_to_int(t2)
return int_to_time(seconds)
start=Time(9,45,00)
running=Time(1,35,00)
done=add_time(start,running)
print(done)
I am new to python and i've been doing some practice lately.I came across a question and i've written the code for the same.But I am repeatedly getting an error: "add_time is not defined". I tried defining a main() method but then it doesn't print anything.Please help.

You haven't created an object to the above class.
Any function/method inside a class can only be accessed by an object of that class .For more information on the fundamentals of Object Oriented Programming, please check this page.
Meanwhile for this to work, define your class in the following way :
class Time:
def __init__(self,x=None,y=None,z=None):
self.hour=x
self.minute=y
self.second=z
def __str__(self):
return "({:02d}:{:02d}:{:02d})".format(self.hour, self.minute, self.second)
def time_to_int(time):
minutes=time.hour*60+time.minute
seconds=minutes*60+time.second
return seconds
def int_to_time(seconds):
time=Time()
minutes,time.second=divmod(seconds,60)
time.hour,time.minute=divmod(minutes,60)
return time
def add_time(t1,t2):
seconds=time_to_int(t1)+time_to_int(t2)
return int_to_time(seconds)
and outside the class block, write the following lines :
TimeObject = Time()
start=Time(9,45,00)
running=Time(1,35,00)
TimeObject.add_time(start,running)
print "done"
I however suggest you to write the add_time function outside the class because you are passing the objects to the class as the parameters to the function within the same class and it is considered as a bad design in object oriented programming.
Hope it helps. Cheers!

This works fine for me as long as you specified 3 args in your constructor
def int_to_time(seconds):
time=Time(0,0,0) # just set your 3 positionals args here
minutes,time.second=divmod(seconds,60)
time.hour,time.minute=divmod(minutes,60)
return time
Another way to avoid it could be:
class Time:
def __init__(self,x=0,y=0,z=0):
self.hour=x
self.minute=y
self.second=z
If you want to add your functions to your class (such as time_to_int, int_to_time or even add_time) then you will need to indent with one more level of 4 spaces and add self to your method parameters

Hii Mathers25,
I solve your problem try this below code to get the best output,
class TimeClass:
def __init__(self,x,y,z):
self.hour = x
self.minute = y
self.second = z
def __str__(self):
return "({:02d}:{:02d}:{:02d})".format(self.hour, self.minute, self.second)
def time_to_int(self,time):
minutes = (time.hour * 60) + time.minute
seconds = (minutes * 60) + time.second
return seconds
def int_to_time(self,seconds):
time = TimeClass(0,0,0)
minutes,time.second=divmod(seconds,60)
time.hour,time.minute=divmod(minutes,60)
return time
def add_time(self,t1,t2):
seconds = self.time_to_int(t1) + self.time_to_int(t2)
# Call method int_to_time() using self keyword.
return self.int_to_time(seconds)
# First time object create that time set value is 0 of hour,minute and second
TimeObject = TimeClass(0,0,0)
# After create second object
start=TimeClass(9,45,00)
# After create thired Object
running=TimeClass(1,35,00)
# Store the value which return by add_time()
done = TimeObject.add_time(start,running)
# Display the value of done variable
print(done)

class Employee:
def __init__(self):
self.wage = 0
self.hours_worked = 0
def calculate_pay(self):
return self.wage * self.hours_worked
alice = Employee()
alice.wage = 9.25
alice.hours_worked = 35
print('Alice:\n Net pay: {:.2f}'.format(alice.calculate_pay()))
barbara = Employee()
barbara.wage = 11.50
barbara.hours_worked = 20
print('Barbara:\n Net pay: {:.2f}'.format(barbara.calculate_pay()))

Works for me:
class C:
def f(a, b):
return a + b
x = f(1,2)
print(C.x)
but you should not do such things. Code in class-level is executing when class is "creating", usually you want static methods or class methods (decorated with #staticmethod or #classmethod) and execute code in some function/instantiated class. Also you can execute it on top (module) level if this is the simple script. Your snippet is "bad practice": class level (i'm talking about indentation) is for declarations, not for execution of something. On class-level is normal to execute code which is analogue of C macros: for example, to call decorator, to transform some method/attribute/etc - static things which are "pure" functions!

why I can't update a variable value and return self.func(*args)?

I'm sending a variable value from programa1 for a new object using :
def send_price(self):
self.pricesend = float(self.text1.get()) #this take a value from a tkinker.Entry
print(self.pricesend)
objetoprograma1.Object(self.pricesend)
the object "objetoprograma1" return a new value using:
class Object():
def __init__(self, price):
self.price_recibe = float(price)
print(self.price_recibe)
self.new_price = self.price_recibe + 10
print(self.new_price)
programa1.Aplication.recibe_newprice(self, float(self.new_price))
now I want to update the value in the principal1 tkinter.Entry called self.text1:
def recibe_newprice(self, new_price):
self.new_price = new_price
print("price new recibe" , self.new_price)
## this don't work.. this don't update or change the value in the tkinter.Entry
self.text1.delete(0, len(self.text1.get()))
self.text1.insert(self.my_main, str(self.new_price))
I have the following exception:
Exception in Tkinter callback
Traceback (most recent call last):
File "C:\Python34\lib\tkinter\__init__.py", line 1482, in __call__
return self.func(*args)
File "B:\MAESTRIA\PYTHON\trabajos\hello\programa1.py", line 38, in send_price
objetoprograma1.Object(self.pricesend)
File "B:\MAESTRIA\PYTHON\trabajos\hello\objetoprograma1.py", line 19, in __init__
programa1.Aplication.recibe_newprice(self, float(self.new_price))
File "B:\MAESTRIA\PYTHON\trabajos\hello\programa1.py", line 51, in recibe_newprice
self.text1.delete(self.my_main, len(self.text1.get()))
AttributeError: 'Object' object has no attribute 'text1'
the full programa1.py
# -*- coding: latin-1 -*-
import tkinter
import objetoprograma1
import time
class Aplication():
def __init__(self,my_main):
self.my_main = my_main
self.variables()
self.GUI()
def variables (self):
self.price = None
self.list = []
def GUI(self):
self.text1 = tkinter.Entry()
self.text1.insert(0, "1000")
self.text1.grid(column = 0, row = 0)
self.boton1 = tkinter.Button(self.my_main, text = "sendprice", command = self.send_price )
self.boton1.grid(column=1, row = 0)
def send_price(self):
self.pricesend = float(self.text1.get())
print(self.pricesend)
objetoprograma1.Object(self.pricesend)
def recibe_newprice(self, new_price):
self.new_price = new_price
print("price new recibe" , self.new_price)
## this don't work
self.text1.delete(0, len(self.text1.get()))
self.text1.insert(self.my_main, str(self.new_price))
if __name__ == "__main__":
root = tkinter.Tk()
#root.geometry("800x500+0+0")
root.title("titulo")
app = Aplication(my_main=root)
root.mainloop()
and objetoprograma1.py
# -*- coding: latin-1 -*-
import programa1
import tkinter
import time
class Object():
def __init__(self, price):
self.price_recibe = float(price)
print(self.price_recibe)
self.new_price = self.price_recibe + 10
print(self.new_price)
programa1.Aplication.recibe_newprice(self, float(self.new_price))

Look at your Object class and look at the exception message. You are calling the recibe_newprice method, but passing it the Object instance (Object has no text1 attribute). The recibe_newprice is written for the Aplication class and as such expects self to be an instance of the Aplication class. You seem to be mixing up what classes are for or how the self argument works.
My first tip is to name things with more descriptive names. Names like Object, Application, and Program1 don't tell the reader anything about what the purpose of those objects are.
Second, do you know the difference between classes and functions? Maybe this will help. I would code the send_price method this way:
def send_price(self, price_recibe):
pricesend = float(self.text1.get())
print(pricesend)
print(price_recibe)
new_price = price_recibe + 10
print(new_price)
self.recibe_newprice(new_price)
If this doesn't make sense why I'm doing things this way or why this might be considered better/easier than the way you did it then I suggest researching how python classes, attribute assignment, and argument passing works.

Time is not defined - Class python

I've been trying to make this class called Time with has the attributes of hour,minutes and seconds, that also has accessor functions and mutator functions such as set_hour, increment_hour and so on.
This is my code, I cannot get it to work I get the error Time is not defined or t is not defined when i switch the last lines around. Python 3.2.5 by the way.
class Time:
"""The Time class defines the time with
attributes: hour, minute, second
"""
#Attributes
hour = 12
minutes = 00
seconds = 00
#Functions
def get_hour(self):
return self.hour
def get_minute(self):
return self.minute
def get_second(self):
return self.second
def print_time(self):
print("Hello, the current time is", self.hour,":",self.minute,":",self.second)
def set_hour(self, new_hour):
self.hour = new_hour
t.set_hour("1")
print(t.get_hour())
print(t.print_time())
t = Time()

It seems you are invoking the method set_hour("1") on a variable t before that variable has been initialized by t = Time().
EDIT: and correct the indentation as said in the comments. I'm not a Python programmer so I didn't catch that.