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I am currently using Codeacademy to learn Python. It is the first language I have ever tried to learn and I am currently stuck. Now I'm not stuck because I couldn't get past a certain lesson. I'm stuck because I had to do a quick search on the internet to find out what the first line of code was supposed to be. It never said anything about that first line anywhere and I want to know what it's supposed to do. Here is the full code when it is completed, correctly:

from datetime import datetime
now = datetime.now()
print now
year = now.year
month = now.month
day = now.day
print year
print month
print day
print str(month) + "/" + str(day) + "/" + str(year)

I kept getting an error telling me that datetime is not defined. I finally found that first line by looking through the Q&A section of Codeacademy.

user3085639
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2 Answers2

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It is an issue with Codeacademy environment. It may be restricted for educational purposes. The import should work in an ordinary Python environment:

from datetime import datetime # import `datetime` class from `datetime` module

print(datetime.utcnow()) # call class method

datetime is a stdlib module. It is always available.

It can also could be written as:

import datetime # import module

print(datetime.datetime.utcnow()) # module.klass.klassmethod()

Rule of thumb for a well-written Python code: unless it is a builtin function or a Python keyword then you could find where any name that is used in the code were introduced just by looking at the source code.

Module names are introduced using import statements at the top of the file with the source code usually.

Make sure there is no datetime.py file in your current working directory if you are trying this code on your local computer. Otherwise import statement will use it instead of the one from stdlib.

jfs
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That first line defines datetime (hence the error). More specifically, it imports the datetime object from the datetime module.

More info here: http://effbot.org/zone/import-confusion.htm

Lenny
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  • Ohh, thanks. I'm a little more confused now because I removed it and everything worked just fine... – user3085639 Dec 10 '13 at 06:33
  • Yeah, the datetime module is definitely a weird one. You just kind of have to think of it as a methods within an object without a module, like datetime (module) -> datetime (object) -> now(method). Most modules aren't designed like that, fortunately! – AaronB Dec 10 '13 at 06:39
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    @AaronB: it is common: `time`, `mmap`, `bisect`, `socket`, `select`, `crypt`, `array`, `dis`, `glob`, `platform` and other stdlib modules have functions/classes with the same names as their parent module. – jfs Dec 11 '13 at 20:19
  • @J.F.Sebastian: I used the word 'most' generally referring to modules that you'd be using as a beginner to Python, but you are absolutely correct that there are quite a few modules in the Python lib with this behavior; thanks! – AaronB Dec 11 '13 at 22:22