Use a lambda and filter(), create a variable high_cal with items in meals where the "calories" 1000

Question

Link to Objective:
http://teamtreehouse.com/library/functional-python/the-lambda-lambada/lambda-2
I've watch the Lambda video time and again.
I've downloaded the zip and looked at the "stock.py" file, but it deals with
json so it really doesn't match up with any of the objectives (that don't mention json at all)
I don't know...all of Kenneth Love's code examples and objective questions seem so obtuse.
The don't really google well.
I didn't have any difficulties with the python in kat chuang's course:
http://teamtreehouse.com/library/data-science-basics
Another thing: 
Did you ever notice that the "preview" (and answer analyzer) for the
python objectives is really awful (either offering nothing or 
no really helpful debugging suggestions)? 
Anyway, here are some of my attempts (tries) 
that all got generic  "Bummer!" errors:
```python
high_cal = meals.filter(lambda x: x[1] > 1000)
high_cal = filter( lambda x:  x[1] > 1000, meals)
high_cal = filter( lambda calories:  calories > 1000, meals)
high_cal = filter( lambda meals:  meals.calories > 1000)
 ```

akak · Accepted Answer

Hey,
You are very close. Last one almost there :) 
Try this: 
python
high_cal = filter(lambda meal: meal['calories'] > 1000, meals)

The first two "meal" could be "x" or in fact almost anything. It's just a name for variable, but you need to point to calories key and then as a second argument for filter put the dict.

james white · Answer

Thanks akak,
I knew it was something simple, but I would have spent hours more researching
before thinking to try some single quotes and some brackets.
I guess: 
meal['calories'] 
..refers to the element of the meals' tuple whose value 
is associated with the variable 'calories'. 
After a bit more research I found this Functional Programming "docs" howto tutorial:
https://docs.python.org/3/howto/functional.html
where there is an example:
```python
import functools
total = functools.reduce(lambda a, b: (0, a[1] + b[1]), items)[1]
```
Which the docs author says (referring to the example lines of code above):
If you try to do too much in a lambda statement, you’ll end up with 
an overly complicated expression that’s hard to read
Maybe this stackoverflow thread has the final word about python lambdas:
http://stackoverflow.com/questions/890128/why-python-lambdas-are-useful
...where someone named "javier" in the first answer says:
lambda is one of the requisites for a readable functional language. 
it's a pity that Python's syntax makes them so limited.
 still, it's miles ahead of any language without it.

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james white

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Use a lambda and filter(), create a variable high_cal with items in meals where the "calories" > 1000

2 Answers

akak

akak

James N

James N

james white

james white