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RE: Fixed-length text file to database script

P: n/a
#your thought is right.
================================================== =====
def sizes2fields(sizes):
d = []
begin = 0
for i in sizes:
if begin:
end = begin + i
else: end = i
d.append((begin, end))
begin += i
return tuple(d)

def slicestring(s, fields):
d = []
for i in fields:
d.append(s[i[0]:i[1]])
return tuple(d)

sizes = [16,4,8,8,8]
s = '1234567890123456789012345678901234567890123456789 01234567890'
print slicestring(s, sizes2fields(sizes))
================================================== ========
prints out:
('1234567890123456', '7890', '12345678', '90123456', '78901234')

hope it helps.
thanks Edwin

-----Original Message-----
From: py************************************************ **@python.org
[mailto:py***************************************** *********@python.org]
On Behalf Of Eric Wertman
Sent: Thursday, August 14, 2008 1:59 PM
To: py*********@python.org
Subject: Re: Fixed-length text file to database script
I have a machine (PLC) that is dumping its test results into a fixed-
length text file.
While it has nothing to do with python, I found that creating a MySQL
table with the proper fixed length char() fields and using 'load data
infile' was the easiest way to deal with that sort of scenario. The
python script is the secondary part, that handles the normalization
and proper typing of the first table to the second, permanent storage
area. But in this case, the more advanced bits are the database and
SQL details, and python is just a very convenient way to build the SQL
statements and execute them.

I'm really not sure what the best way to deal with fixed length data
is in python. I might define a list with the field lengths and use a
string slicing to get the items.. as a first thought:

myfile = '/somewhere/somefile.txt'
sizes = [16,4,8,8,8]

fd = open(myfile,r)

for line in fd.readlines() :

idx1 = 0
for l in sizes :
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Aug 14 '08 #1
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2 Replies


P: n/a
On Aug 15, 4:55 am, Edwin.Mad...@VerizonWireless.com wrote:
#your thought is right.
================================================== =====
def sizes2fields(sizes):
d = []
begin = 0
for i in sizes:
if begin:
end = begin + i
else: end = i
d.append((begin, end))
begin += i
return tuple(d)
Those who are not paid by the keystroke and/or prefer to expend
keystrokes on meaningful names might like an alternative like this:
def sizes2offsets(sizes):
offsets = []
begin = 0
for size in sizes:
end = begin + size
offsets.append((begin, end))
begin = end
return offsets
Aug 15 '08 #2

P: n/a
Lie
On Aug 15, 7:12*am, John Machin <sjmac...@lexicon.netwrote:
On Aug 15, 4:55 am, Edwin.Mad...@VerizonWireless.com wrote:
#your thought is right.
================================================== =====
def sizes2fields(sizes):
* *d = []
* *begin = 0
* *for i in sizes:
* * * if begin:
* * * * *end = begin + i
* * * else: end = i
* * * d.append((begin, end))
* * * begin += i
* *return tuple(d)

Those who are not paid by the keystroke and/or prefer to expend
keystrokes on meaningful names might like an alternative like this:
def sizes2offsets(sizes):
* offsets = []
* begin = 0
* for size in sizes:
* * end = begin + size
* * offsets.append((begin, end))
* * begin = end
* return offsets
This is even shorter: (and IMHO, clearer)

def split(s, fields):
ret = []
for field in fields:
s, d = s[field:], s[:field]
ret.append(d)
return ret

sizes = [16, 4, 8, 8, 8]
s = '1234567890123456789012345678901234567890123456789 01234567890'
print split(s, sizes)

alternatively, if what you've got is the partition position instead of
field width:

def split(s, sizes):
ret = []
start = sizes[0]
for end in sizes[1:]:
r, start = s[start: end], end
ret.append(r)
return ret

sizes = [0, 16, 20, 28, 36, 44]
s = '1234567890123456789012345678901234567890123456789 01234567890'
print split(s, sizes)

Michael Stroder:
If the input data has to be pre-processed before storing it into the
database a Python script would be needed.
But not for converting the fixed length string, you could just have
SQL process the fixed length string then retrieve it back as separate
fields.
Aug 15 '08 #3

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