I need some help with Sets.py

Question

I used the script below however when I tried in Python shell it gave me an empty list but Treehouse has accepted. .
Can anyone give me advice ? https://www.python.org/shell/
```sets.py
COURSES = {
    "Python Basics": {"Python", "functions", "variables",
                      "booleans", "integers", "floats",
                      "arrays", "strings", "exceptions",
                      "conditions", "input", "loops"},
    "Java Basics": {"Java", "strings", "variables",
                    "input", "exceptions", "integers",
                    "booleans", "loops"},
    "PHP Basics": {"PHP", "variables", "conditions",
                   "integers", "floats", "strings",
                   "booleans", "HTML"},
    "Ruby Basics": {"Ruby", "strings", "floats",
                    "integers", "conditions",
                    "functions", "input"}
}
def covers(param):
    returnable = []
    for course in COURSES:
        if COURSES[course] & param:
            returnable.append(course)
    return returnable
```

Jon Mirow · Accepted Answer

Hi there, 
Works fine for me (good job!)... how are you passing the set into the function? Are you calling set() on the string to search for?  I'm sorry if that's not it,  it's just  the only thing I can think of other than typo's or case sensativity... if it doesn't apply, just skip this! lol. 
To explain what I mean, say I wanted to pass "Python" into the covers() function. covers() expects a set, so I have to convert the string "Python" to a set: 
If I pass in "Python" like this:
python
course = covers({"python"})
print(course)

It'll return the correct output, however if I typed it like this:
python
course = covers(set("Python"))
print(course)

I'd get an empty list. The reason is the set() takes an iterable object and turns it into a set. A string is an iterable, so set("python") would result in something like this:
```python
set("Python")
{'t', 'P', 'n', 'o', 'y', 'h'}

And of course, none of those strings match any strings in the COURSES values, so the list is empty. To get a set that ends up as {"Python"} you can do one of the following:
python
covers({"Python"})    # Just write the set literal
covers(set(["Python"]))    # Wrapped in a list
covers(set(("python",)))    # Wrapped in a tuple, note the comma
```
You can even pass a dictionary to set() and get a dictionary of the keys... although as keys are already unique that's usually kind of pointless, but again, could be useful if you wanted to use set methods on dictionary keys :)
Hope it helps!

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Andras Andras

Andras Andras

I need some help with Sets.py

1 Answer

Jon Mirow

Jon Mirow

Andras Andras

Andras Andras