Python concatenation of string

Question

I'm doing python programming and this is class unit of that. and the code is not printing the right answer.

class Car(object):
    condition = "new"
    def __init__(self, model, color, mpg):
        self.model = model
        self.color = color
        self.mpg   = mpg
    def display_car(self):
        print "This is a "+ self.color + self.model+ " with "+str(self.mpg)+"MPG"

my_car = Car("DeLorean", "silver", 88)
print my_car.display_car()

I'm trying to print This is a silver DeLorean with 88 MPG.

Kaushik, also add spaces: `'...self.color + " " +self.model...'` — Grijesh Chauhan, Aug 20 '13 at 19:13

alecxe · Accepted Answer · 2013-08-20T19:15:01.647

5

Try this version of display_car method instead:

def display_car(self):
    print "This is a %s %s with %d MPG." % (self.color, self.model, self.mpg)

Or, you can make use of format:

def display_car(self):
    print "This is a {0} {1} with {2} MPG.".format(self.color, self.model, self.mpg)

Both versions print This is a silver DeLorean with 88 MPG.

I think you see that both versions are more readable than your's with string concatenation.

You can make it even more readable by using format with named arguments:

def display_car(self):
    print "This is a {color} {model} with {mpg} MPG.".format(color=self.color, model=self.model, mpg=self.mpg)

Also, you have None printed too - replace print my_car.display_car() with my_car.display_car().

edited Aug 20 '13 at 19:15

answered Aug 20 '13 at 19:08

alecxe

462,703
120
1,088
1,195

1

better to use `string.format()` ? and its should be `%d` for `mpg`? – Grijesh Chauhan Aug 20 '13 at 19:15
@alecxe I would like to know my concatenation statement is right or not ? if i wanna `print` **This is a silver DeLorean with 88 MPG** with spaces in them only one after one word – Aug 20 '13 at 19:16
@GrijeshChauhan yup, I've added options using `format`. `%d` might be more correct here, agreed. Thanks. – alecxe Aug 20 '13 at 19:18
@Kaushik your concatenation statement is almost right except that you are missing whitespaces. It's better to use options I've mentioned - less error prompt and more readable. – alecxe Aug 20 '13 at 19:19
I am reader on Python tag (rarely answers as new learner). So I have a question `%s` will behave correctly with `mpg` (auto typecasting happens?) – Grijesh Chauhan Aug 20 '13 at 19:20
1

Well, take a look http://stackoverflow.com/questions/15170349/whats-the-difference-between-r-s-and-d-in-python and http://stackoverflow.com/questions/4288973/s-and-d-python. – alecxe Aug 20 '13 at 19:22
@alecxe Ok Boss I'll take care of It . Thanks Once again. – Aug 20 '13 at 19:24

score 4 · Answer 2 · answered Aug 20 '13 at 19:10

Change this:

def display_car(self):
    return "This is a "+ self.color + self.model+ " with "+str(self.mpg)+"MPG"

You see, the display_car method must return the value to print. Alternatively, you could leave display_car() as it is, but instead call the method like this:

my_car = Car("DeLorean", "silver", 88)
my_car.display_car()

score 1 · Answer 3 · answered Aug 20 '13 at 19:08

1

The print in print my_car.display_car() is redundant because you've already printed the statement in the display_car method. Thus, you get an extra None.

answered Aug 20 '13 at 19:08

Benjamin Peterson

19,297
6
32
39

so what should i do ? the `display_car` method `print` statement should be replaced by `return`? – Aug 20 '13 at 19:12
That's one option. Alternatively, just write `my_car.display_car()` (without of the `print` in front). – Benjamin Peterson Aug 20 '13 at 19:14

score 1 · Answer 4 · answered Aug 20 '13 at 19:10

1

Python implicitly returns None if you don't return anything so printing a function that calls print will also print None.

answered Aug 20 '13 at 19:10

Phillip Cloud

24,919
11
68
88

score 0 · Answer 5 · edited Aug 20 '13 at 19:47

0

The line

print my_car.display_car()

should be

my_car.display_car()

edited Aug 20 '13 at 19:47

Edward

3,292
1
27
38

answered Aug 20 '13 at 19:22

misalabs

11
1

Python concatenation of string

5 Answers5