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Manipulating date and time using Python in NiceForm and NiceLabel Portal

Time values are represented with the time class. Times have attributes for hour, minute, second, and microsecond. They can also include time zone information. A time instance only holds values of time, and not a date associated with the time.

from datetime import datetime;

time1 = datetime.time(datetime.now()); # Get current time
h = time1.hour;
m = time1.minute;
s = time1.second;
ms = time1.microsecond;
tz = time1.tzinfo;
min = time1.min;
max = time1.max;

d1.Value = "Hour: " + str(h);
d2.Value = "Minute: " + str(m);
d3.Value = "Second: " + str(s);
d4.Value = "Microsecond: " + str(ms);
d5.Value = "Time zone: " + str(tz);
d6.Value = "Earliest: " + str(min);
d7.Value = "Latest: " + str(max);

Calendar date values are represented with the date class. Instances have attributes for year, month, and day. It is easy to create a date representing current date using the today() class method. As with time, the range of date values supported can be determined using the min and max attributes.

from datetime import date;

date1 = date.today(); # Get current date
year = date1.year;
month = date1.month;
day = date1.day;
ordinal = date1.toordinal();
min = date1.min;
max = date1.max;

d1.Value = "Day: " + str(day);
d2.Value = "Month: " + str(month);
d3.Value = "Year: " + str(year);
d4.Value = "Ordinal: " + str(ordinal);
d5.Value = "Earliest: " + str(min);
d6.Value = "Latest: " + str(max);

How can I add or subtract from a date?

To add or subtract from a date use the datetime.timedelta object.

from datetime import datetime, timedelta, time;

time1 = datetime.now();
diff = timedelta(weeks=52);  # 1 year
time2 = time1 + diff;
diff = timedelta(days=730);  # 2 years
time3 = time1 + diff;
diff = timedelta(hours=240);  # 10 days
time4 = time1 + diff;
diff = timedelta(weeks=40, days=84, hours=23, minutes=50, seconds=600);  # Adds up to 365 days
time5 = time1 - diff;

d1.Value = "Current date and time: " + str(time1);
d2.Value = "Added 52 weeks (1 year): " + str(time2);
d3.Value = "Added 730 days (2 years): " + str(time3);
d4.Value = "Added 10 days: " + str(time4);
d5.Value = "Subtracted 365 days: " + str(time5);

How can I calculate difference of two dates?

When two dates are subtracted they produce timedeltas.

from datetime import date;

date1 = date.today();
date2 = date(1973, 7, 6);
diff = date1 - date2;

d1.Value = "Current date: " + str(date1);
d2.Value = "My birthday: " + str(date2);
d3.Value = "I am : " + str(diff.days) + " days old.";

Can I compare date or time values?

Both time and date values can be compared using standard operators to determine which one is earlier or later.

from datetime import date, time;

date1 = date.today();
date2 = date(1973, 7, 6);
time1 = time(12, 0, 0);
time2 = time(13, 5, 0);

d1.Value = "Date 1: " + str(date1);
d2.Value = "Date 2: " + str(date2);
d3.Value = "Date 1 < Date 2: " + str(date1 < date2);
d4.Value = "Time 1: " + str(time1);
d5.Value = "Time 2: " + str(time2);

d6.Value = "Time 1 > Time 2: " + str(time1 < time2);

How can I replace just part of date?

from datetime import datetime;

date1 = datetime.now();            # Use current date and time
date2 = date1.replace(year=2012);  # Change year to 2012
date3 = date1.replace(month=12);   # Change month to December
date4 = date1.replace(day=31);     # Change day to 31
date5 = date1.replace(day=31, month=12, year=2012); # Change day, month and year all at once.

d1.Value = str(date1);
d2.Value = str(date2);
d3.Value = str(date3);
d4.Value = str(date4);
d5.Value = str(date5);

Formatting time and date

Default string representation of a datetime object uses the ISO 8601 format (YYYY-MM-DDHH:MM:SS.mmmmmm). Other formats can be generated using strftime() method. The following directives can be embedded in the format string:

Here are some examples of using different directives:

from datetime import date;

format1 = "%A,  %B %d, %Y";
format2 = "Today is day %j of the year.";
format3 = "Short month name: %b; Short weekday name: %a";

date1 = date.today();
d1.Value = date1.strftime(format1);
d2.Value = date1.strftime(format2);
d3.Value = date1.strftime(format3);

How can I get a week number from a date?

from datetime import date;

format = "Today is day %w of the %W week of the year.";

date1 = date.today();
d1.Value = date1.strftime(format);

All code samples above should work in NiceForm and NiceLabel Portal. You can find all samples in sample form file (PyDateTime.xff).

Working with Modules in Python Scripts in NiceForm and NiceLabel Portal

A module is a Python source file (a text file) whose name ends in .py. Objects (names) defined in a module can be imported and used elsewhere.

The import statement has several different forms:

import module
from module import name1, name2
from module import name as anotherName
from module import *

If you use the first form, you receive a reference to the module object. If a module defines a class SomeClass then you can access it using module.SomeClass. If you need access to only a few objects from the module, you can use the second form. It imports only the names you have specified from the module. If a name you wish to import would clash with a name in your current namespace, you can use the third form. The fourth form imports all the names from the module into your namespace. In Python this is something you would not normally do.

Exploring Modules

To find out what a module contains you can use the dir() function, which lists all the attributes of an object and therefore all functions, classes, variables of a module. Several of these names begin with an underscore which means that they are not meant to be used outside the module.

For example:

import math
print dir(math)

would return the following:

['__doc__', '__name__', '__package__', 'acos', 'acosh', 'asin', 'asinh', 'atan', 'atan2', 'atanh', 'ceil', 'copysign', 'cos', 'cosh', 'degrees', 'e', 'erf', 'erfc', 'exp', 'expm1', 'fabs', 'factorial', 'floor', 'fmod', 'frexp', 'fsum', 'gamma', 'hypot', 'isinf', 'isnan', 'ldexp', 'lgamma', 'log', 'log10', 'log1p', 'modf', 'pi', 'pow', 'radians', 'sin', 'sinh', 'sqrt', 'tan', 'tanh', 'trunc']

Very useful command that can help you while exploring modules, classes, variables and methods is help(). help() is a built-in function that provides information like what method does and what arguments that method takes.

import math
help(math.sin)

would return:

sin(...)
    sin(x)

    Return the sine of x (measured in radians).

Finding modules

To import a module, the Python interpreter needs to find it. With a module, the Python interpreter first looks for a file named module.py, where module is the name of the module you pass to the import statement. The Python interpreter looks for modules in the directories that are part of the module search path. These directories are listed in the sys.path variable from the sys module.

import sys
print sys.path

There are some differences between NiceForm and NiceLabel Portal here. In NiceForm you would get something like this:

['C:\Windows\system32\python27.zip','C:\Ln\Python27\Lib', 'C:\Ln\Python27\DLLs', 'C:\Ln\Python27\Lib\lib-tk','C:\PROGRA~2\EuroPlus\NICELA~1\bin','C:\Ln\Python27', 'C:\Ln\Python27\lib\site-packages', 'C:\Ln\Python27\lib\site-packages\win32', 'C:\Ln\Python27\lib\site-packages\win32\lib', 'C:\Ln\Python27\lib\site-packages\Pythonwin']

while in NiceLabel Portal sys.path would return just ‘.’. The reason for this is that NiceLabel Portal runs in the web browser and does not have access to the local files and directories. As a consequence in NiceLabel Portal you can use only built-in modules. You have on other hand have access to a rich functionality of .NET Framework Class Library for Silverlight.