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def FileCheck(fn): try: fn=open("TestFile.txt","U") except IOError: print "Error: File does not appear to exist." return 0 I'm trying to make a function that checks to see if a file exists and if doesn't then it should print the error message and return 0 . Why isn't this working??? You'll need to indent the return 0 if you want to return from within the except block. Also, your argument isn't doing much of anything. Instead of assigning it the filehandle, I assume you want this function to be able to test any file? If not, you don't need any arguments. def FileCheck(fn): try: open(fn, "r")

I am a beginner in Python and have been testing different kinds of sample code. When I started using Python3 instead of 2.7; I came upon a syntax error, but I don't understand how to fix that error. File "app.py", line 101 except InvalidUserPass, e: ^ SyntaxError: invalid syntax Here is more of that code to give some context: @app.route('/login/', methods=['GET', 'POST']) def login(): error = None if request.method == 'POST': session['username'] = request.form['username'] session['password'] = request.form['password'] try: # use reddit_api's login r.login(user=session['username'], password

Is this the right way to use the python "with" statement in combination with a try-except block?: try: with open("file", "r") as f: line = f.readline() except IOError: <whatever> If it is, then considering the old way of doing things: try: f = open("file", "r") line = f.readline() except IOError: <whatever> finally: f.close() Is the primary benefit of the "with" statement here that we can get rid of three lines of code? It doesn't seem that compelling to me for this use case (though I understand that the "with" statement has other uses). EDIT: Is the functionality of the above two blocks of

I've got a class: class ThisClass { private string a {get; set;} private string b {get; set;} } I would like to use the Intersect and Except methods of Linq, i.e.: private List<ThisClass> foo = new List<ThisClass>(); private List<ThisClass> bar = new List<ThisClass>(); Then I fill the two lists separately. I'd like to do, for example (and I know this isn't right, just pseudo code), the following: foo[a].Intersect(bar[a]); How would I do this? Maybe // returns list of intersecting property 'a' values foo.Select(f => f.a).Intersect(bar.Select(b => b.a)); BTW property a should be public. If you

I have a nested dictionary. Is there only one way to get values out safely? try: example_dict['key1']['key2'] except KeyError: pass Or maybe python has a method like get() for nested dictionary ? unutbu You could use get twice: example_dict.get('key1', {}).get('key2') This will return None if either key1 or key2 does not exist. Note that this could still raise an AttributeError if example_dict['key1'] exists but is not a dict (or a dict-like object with a get method). The try..except code you posted would raise a TypeError instead if example_dict['key1'] is unsubscriptable. Another difference

This query works: mysql> SELECT s.sno FROM students s; +------+ | sno | +------+ | 1 | | 2 | | 3 | | 4 | | 5 | | 6 | | 7 | | 8 | | 9 | | 10 | +------+ 10 rows in set (0.00 sec) This query also works: mysql> SELECT t.sno FROM take t WHERE t.cno = 'CS112'; +------+ | sno | +------+ | 1 | | 2 | | 3 | | 4 | +------+ 4 rows in set (0.00 sec) BUT this query: SELECT s.sno FROM students s EXCEPT SELECT t.sno FROM take t WHERE t.cno = 'CS112'; fails with the error: mysql> SELECT s.sno FROM students s -> EXCEPT -> SELECT t.sno FROM take t WHERE t.cno = 'CS112'; ERROR 1064 (42000): You have an error in