newbie problem with a hash

[Graham Nicholls]

I've got a file which I've read in and split to make a hash like this:


def initialize(fname)
@data=Hash.new
begin
IO.foreach(fname) do |line|
key,value=line.chomp.split(":")
@data[key]=value
end
end

This gives a hash keyed on the first field of the file, where : is the
separator. (NB How do I handle : in the data - prompt to self!)

But when I try to get the value associated with that key by a fetch, I get
and IndexError:

def get_datum(datid) # Typical datid is $01 - I've stripped off the colon.
if $debug
print("Getting data for id [#{datid}]\n") # Prints $01
end

begin
#@data.fetch("$01") - this works OK,
@data.fetch(datid) # This causes an IndexError
rescue IndexError => err
print("No data for key [#{datid}] : #{err}\n")
@data.each do |key,val|
printf("Key [%s] => [%s]\n",key,val) # Shows $01 => avalue (amongst
others)
end
exit(NO_DATA)
end
end

I'm racking my brains, but to no avail. If I put the key in as a literal,
it returns, but using the datid variable, I get an IndexError.

I'd appreciate a pointer - its probably something daft - it usually is, but
I haven't got a cardboard analyst.

PS I rather like Ruby - its more elegant than Python (but don't tell anyone
in c.l.python!), IMNSHO.
Graham

 

[Sean O'Dell]

I've got a file which I've read in and split to make a hash like this:


def initialize(fname)
@data=Hash.new
begin
IO.foreach(fname) do |line|
key,value=line.chomp.split(":")
@data[key]=value
end
end

This gives a hash keyed on the first field of the file, where : is the
separator. (NB How do I handle : in the data - prompt to self!)

But when I try to get the value associated with that key by a fetch, I get
and IndexError:

def get_datum(datid) # Typical datid is $01 - I've stripped off the colon.
if $debug
print("Getting data for id [#{datid}]\n") # Prints $01
end

begin
#@data.fetch("$01") - this works OK,
@data.fetch(datid) # This causes an IndexError
rescue IndexError => err
print("No data for key [#{datid}] : #{err}\n")
@data.each do |key,val|
printf("Key [%s] => [%s]\n",key,val) # Shows $01 => avalue
(amongst others)
end
exit(NO_DATA)
end
end

I'm racking my brains, but to no avail. If I put the key in as a literal,
it returns, but using the datid variable, I get an IndexError.

How are you calling get_datum? Show us the line where you call it that gives
you that error.

Sean O'Dell

 

[Mark Hubbart]

I've got a file which I've read in and split to make a hash like this:


def initialize(fname)
@data=Hash.new
begin
IO.foreach(fname) do |line|
key,value=line.chomp.split(":")
@data[key]=value
end
end

This gives a hash keyed on the first field of the file, where : is the
separator. (NB How do I handle : in the data - prompt to
self!)

But when I try to get the value associated with that key by a fetch, I
get
and IndexError:

def get_datum(datid) # Typical datid is $01 - I've stripped off the
colon.
if $debug
print("Getting data for id [#{datid}]\n") # Prints $01
end

begin
#@data.fetch("$01") - this works OK,
@data.fetch(datid) # This causes an IndexError
rescue IndexError => err
print("No data for key [#{datid}] : #{err}\n")
@data.each do |key,val|
printf("Key [%s] => [%s]\n",key,val) # Shows $01 => avalue
(amongst
others)
end
exit(NO_DATA)
end
end

Where did you get 'datid'? Are you absolutely positive it's a String? I
would suggest inspect()ing the variable in the debug statement. In
fact, I would suggest doing several tests on the contents of the
variable there, printing out datid.class, (datid =~ /\A\$\d\d\z/),
etc...

and, (less importantly) I would remove some code there, just to make
less code to check

def get_datum(datid)
if $debug
puts "Getting data for id [#{datid.inspect}]" # inspect it
puts "class: #{datid.class}" # check the class
puts "valid? #{datid =~ /\A\$\d\d\z/}" # check via regexp matching
puts "@data.has_key? #{@data.has_key? datid}" # is there a key
there?
end
@data.fetch(datid)
rescue IndexError => err
puts "No data for key [#{datid}] : #{err}"
@data.each {|k,v| puts "Key #{k} => #{v}"}
end

I'm racking my brains, but to no avail. If I put the key in as a
literal,
it returns, but using the datid variable, I get an IndexError.

There really should be absolutely no difference between using a
variable and using a literal... I strongly suspect that somehow you are
not getting the data your function expects.

Oh, and "Welcome!"

HTH,
Mark

 

[Graham Nicholls]

I've got a file which I've read in and split to make a hash like this:


def initialize(fname)
@data=Hash.new
begin
IO.foreach(fname) do |line|
key,value=line.chomp.split(":")
@data[key]=value
end
end

This gives a hash keyed on the first field of the file, where : is the
separator. (NB How do I handle : in the data - prompt to
self!)

But when I try to get the value associated with that key by a fetch, I
get and IndexError:

def get_datum(datid) # Typical datid is $01 - I've stripped off the
colon.
if $debug
print("Getting data for id [#{datid}]\n") # Prints $01
end

begin
#@data.fetch("$01") - this works OK,
@data.fetch(datid) # This causes an IndexError
rescue IndexError => err
print("No data for key [#{datid}] : #{err}\n")
@data.each do |key,val|
printf("Key [%s] => [%s]\n",key,val) # Shows $01 => avalue
(amongst others)
end
exit(NO_DATA)
end
end

I'm racking my brains, but to no avail. If I put the key in as a
literal, it returns, but using the datid variable, I get an IndexError.

How are you calling get_datum? Show us the line where you call it that
gives you that error.

Sean O'Dell

printf("%s",datid.class)

told me it was an array - what a nitwit! Now sorted.
Thanks, both.
Graham