this does not pass:

def area(position):
return position[0] * position[1]

areas = map(area, dimensions)

Question

I don't understand why this does not pass.
```maps.py
dimensions = [
    (5, 5),
    (10, 10),
    (2.2, 2.3),
    (100, 100),
    (8, 70),
]
def area(position):
   return position[0] * position[1]
areas = map(area, dimensions)
```

Jesse Pavlis · Accepted Answer

Hey Grégoire Mesnil,
The requirement for the second Challenge is to use List Comprehension (https://docs.python.org/2/tutorial/datastructures.html#list-comprehensions). You are instead using the built-in function map(). I applaud your usage of python's built-in functions, and this is a good implementation of it, but the task requires the use of list comprehension.
python
areas = [position[0] * position[1] for position in dimensions]

Trike Whipcat · Answer

Wow, I wish this example explicitly stated to use a list comprehension from the outset on task 1. The posted solution raises a type error on my local machine. 
python
def area(dimensions):
    return dimensions[0] * dimensions[1]

area(dimensions)
TypeError: can't multiply sequence by non-int of type 'tuple'
This is attempting to multiply two tuples together: (5, 5) x (10, 10)
Wouldn't this have to be (dimensions[0][0])*(dimensions[0][1])?
I solved it using a function and got the expected results, but I know I'm missing the point of the exercise by not using map or list comprehensions.
```python
def area2(arg):
    result=[]
    for x,y in arg:
        result.append(x*y)
    return result
def area(dimensions):
    return dimensions[0] * dimensions[1]
areas = [area(x) for x in dimensions]
print(area2(dimensions)==areas)
```

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Grégoire Mesnil

Grégoire Mesnil

this does not pass: def area(position): return position[0] * position[1] areas = map(area, dimensions)

2 Answers

Jesse Pavlis

Jesse Pavlis

Grégoire Mesnil

Grégoire Mesnil

Trike Whipcat

Trike Whipcat