SyntaxError when adding to a global set inside a function (Python)

Question

I am trying to write a function that reads keywords from a file (in the format that each keyword is on a new line inside the text file)

I want the function to put the keywords into a global set() called "desiredItems".

desiredItems = set()

def populateDesired():
    for line in open("desireditems.txt"):
        addableLine = line.rstrip("\n")
        global desiredItems.add(addableLine)

For some reason my development environment (Pycharm) tells me that desiredItems.add is invalid syntax.

(sorry If I have inserted code snippet incorrectly etc)

Thanks in advance

I would imagine `set.add()` returns `None` so essentially you are using `global None`. You should just use `global desiredItems` and do the add on the next line. Although I would strongly recommend not using `global` and passing the set in as a parameter. — kylieCatt, Nov 25 '14 at 06:05
@IanAuld, that would be a runtime error. In fact `global` must be followed by one or more _identifiers_, so the `.` causes it to be a syntax error — John La Rooy, Nov 25 '14 at 06:11

score 0 · Answer 1 · answered Nov 25 '14 at 06:03

0

You don't need to use global at all, just remove it.

answered Nov 25 '14 at 06:03

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score 0 · Answer 2 · answered Nov 25 '14 at 06:07

If you need to modify the binding of a global variable, the syntax is like this

def populateDesired():
    global desiredItems
    for line in open("desireditems.txt"):
        addableLine = line.rstrip("\n")
        desiredItems.add(addableLine)

Since you are not modifying the binding - merely calling a method, there is no need for global here at all

def populateDesired():
    for line in open("desireditems.txt"):
        addableLine = line.rstrip("\n")
        desiredItems.add(addableLine)

thank you. I had "modifying the binding" confused with "modifying the set". — Benjels, Nov 25 '14 at 06:20

SyntaxError when adding to a global set inside a function (Python)

2 Answers2