scoping problem with list comprehension // learning Python

[Adrian Dragulescu]

I just started to learn python (first posting to the list).

I have a list of dates as strings that I want to convert to a
list of datetime objects. Here is my debugging session from inside a
method.

(Pdb) formatIndex
'%Y-%m-%d'
(Pdb) [datetime.strptime(i, formatIndex) for i in self.index[0:3]]
*** NameError: global name 'formatIndex' is not defined
(Pdb) [datetime.strptime(i, '%Y-%m-%d') for i in self.index[0:3]]
[datetime.datetime(2007, 1, 3, 0, 0), datetime.datetime(2007, 1, 4, 0, 0),
datetime.datetime(2007, 1, 5, 0, 0)]
(Pdb)

How come I get an error that formatIndex is not defined? I just show that
it has value '%Y-%m-%d', in the same method scope. Not sure why it says
"global name", as I am in a method.

If I run it as a stand-alone, it works:
index = ['2007-01-01', '2007-01-02', '2007-01-03']
formatIndex = '%Y-%m-%d'
print([datetime.strptime(i, formatIndex) for i in index])

Any suggestions much appreciated. I'm sure it's something trivial. I'm
using Python30.

Adrian

 

[Diez B. Roggisch]

I just started to learn python (first posting to the list).

I have a list of dates as strings that I want to convert to a list of
datetime objects. Here is my debugging session from inside a method.

(Pdb) formatIndex
'%Y-%m-%d'
(Pdb) [datetime.strptime(i, formatIndex) for i in self.index[0:3]]
*** NameError: global name 'formatIndex' is not defined
(Pdb) [datetime.strptime(i, '%Y-%m-%d') for i in self.index[0:3]]
[datetime.datetime(2007, 1, 3, 0, 0), datetime.datetime(2007, 1, 4, 0,
0), datetime.datetime(2007, 1, 5, 0, 0)]
(Pdb)

How come I get an error that formatIndex is not defined? I just show
that it has value '%Y-%m-%d', in the same method scope. Not sure why it
says "global name", as I am in a method.

If I run it as a stand-alone, it works:
index = ['2007-01-01', '2007-01-02', '2007-01-03']
formatIndex = '%Y-%m-%d'
print([datetime.strptime(i, formatIndex) for i in index])

Any suggestions much appreciated. I'm sure it's something trivial. I'm
using Python30.

I think your problem here is Pdb. You can't always assume that scoping
and assignment works there as desired.

If you do the same in the interpreter instead of Pdb, does it work? It
works for me in Py2.5, don't have a 3.0 handy.

Diez