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Python Python Basics (2015) Logic in Python Fully Functional

Posted by JoAnna Black
JoAnna Black
659 Points

Python Basics: Fully Functional video: how does .lower work?

I was curious what the .lower bit of code does when it was attached to an argument in the function lumberjack(). I tried taking it out but that caused an error I didn't understand. When I looked up .lower, I could only find information on how this works with strings, as in it will return a lowercase version of the string.

Any help on what this does would be cool, Kenneth doesn't really explain it in the video.

def hows_the_parrot():
    print("He's pining for the fjords!")

hows_the_parrot()

def lumberjack(name, pronoun):
    if name.lower() == "joanna":
        print("JoAnna's a lumberjack and she's OK!")
    else:
        print("{} sleeps all night and {} works all day!".format(name, name))

lumberjack("Greg")

3 Answers

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,457 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,457 Points

The .lower() is a method on a string object. in the your code, name.lower() says call the lower() method on the object name. If name is a string it will call the inherited built-in method to return a copy of the string object name with all the characters changed to lowercase. The object name is not affected:

>>> foo = "STRING"  # define a string object
>>> foo.lower()  # call the lower() method
'string'  # returns a lowercased copy of object
>>> foo
'STRING'  # original string object not affected

If name was not a string object, then an error would be raised:

>>> name = 45
>>> name.lower()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: 'int' object has no attribute 'lower'
JoAnna Black
JoAnna Black
659 Points

Thanks, after stepping away from this last night and looking at it again today it makes sense why you would want to use something like this in your code, but it would have been nice if the video explained it instead of just putting it in there without really saying how that method works or what the functionality is within the example.

Gavin Ralston
Gavin Ralston
28,770 Points
Gavin Ralston
Gavin Ralston
28,770 Points

Just as an aside, remember you can always call help at the python interactive line when you're not sure what a function does.

help(str.lower)

Which would have brought you to a screen like this:

Help on method_descriptor:

lower(...)
    S.lower() -> string

    Return a copy of the string S converted to lowercase.

That would have provided that information for you pretty clearly.

This is exactly the place you want to ask questions like this, so I'm not trying to be glib or anything. Just pointing you in the right direction to get your answer quickly.

If you weren't exactly sure what the variable was you could have done something like this, too:

name = "Joanna"
help(name.lower)

The help function there would have figured out name was a string, then given you the help information for the lower() function you called on it.

jason chan
jason chan
31,009 Points
jason chan
jason chan
31,009 Points

lower converts the entire string to lower case. Because python is probably a case sensitive programming language. It has to do with passwords.

Example.

a = A

if a == a:
    print("true");
else:
    print("false")

// stuff like HelLo would not work to lower would convert everything lower case so things would not be case sensitive for a search.