Re: Python newbie question re Strings and integers
rmac a écrit : Ah! Arghh!!! You are so correct on the usage of the ':' Python syntax is a little different from what I am used to. I don't know what you're used to, but chances are that more than the syntax differs !-) -- http://mail.python.org/mailman/listinfo/python-list
Re: Python newbie question re Strings and integers
rmac a écrit :
the following code attempts to extract a symbol name from a string:
extensionStart = int(filename.rfind('.'))
rfind returns an int, so passing it to the int type constructor is useless.
filenameStart = int(filename.rfind('/'))
idem
#print 'Extension Start - ' + str(extensionStart)
The print statement isn't restricted to string objects. And FWIW, you
can use string formating. The above should be either
print Extension start - , extensionStart
or
print Extension start - %s % extensionStart
As a side not, the naming convention in Python is to use all_lower for
identifiers.
#print 'FileName Start - ' + str(filenameStart)
idem.
currentSymbol=filename[int(filenameStart),int(extensionStart)]
Two more useless int constructor calls.
Uncommenting the print statements clearly show the values to be
integers
If by 'the values', you mean objects bound to identifiers
'filenameStart' and 'extensionStart', I fail to see how they could be
anything else...
(and without the str casts actually provide int+string
errors)
Indeed. What should be the semantic of expression
'answer is ' + 42
???
However, executing this code results in...
opening - /Users/rmac/Documents/Sandbox/data/MarketData/AA.csv
Traceback (most recent call last):
File rHistFileToDB_Equities.py, line 25, in module
currentSymbol=filename[int(filenameStart),int(extensionStart)]
TypeError: string indices must be integers
the expression:
int(filenameStart),int(extensionStart)
1/ takes the object currently bound to identifier 'filenameStart' and
pass it to the int type constructor
2/ takes the object currently bound to identifier 'extensionStart' and
pass it to the int type constructor
3/ build a tuple (actually, a pair of ints) from the results of the two
above expressions
Then you try to use this tuple as an index on a string. A tuple is not a
legal type for string (or any other sequence) subscripting.
The complete syntax for string subscripting is described in the
FineManual. To make a long story short, it's :
string[start:end:step]
where end and step are optionals.
IOW, the correct syntax here is:
filename[filenameStart:extensionStart]
Now, while this is the correct *syntax*, it's not the correct *idiom*.
There's a module named os.path, which provides the needed service. I
leave it up to you to read the relevant part of the documentation...
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Python newbie question re Strings and integers
the following code attempts to extract a symbol name from a string:
extensionStart = int(filename.rfind('.'))
filenameStart = int(filename.rfind('/'))
#print 'Extension Start - ' + str(extensionStart)
#print 'FileName Start - ' + str(filenameStart)
currentSymbol=filename[int(filenameStart),int(extensionStart)]
Uncommenting the print statements clearly show the values to be
integers (and without the str casts actually provide int+string
errors)
However, executing this code results in...
opening - /Users/rmac/Documents/Sandbox/data/MarketData/AA.csv
Traceback (most recent call last):
File rHistFileToDB_Equities.py, line 25, in module
currentSymbol=filename[int(filenameStart),int(extensionStart)]
TypeError: string indices must be integers
Running Python 2.5.2_5 on OSX
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Re: Python newbie question re Strings and integers
rmac wrote:
the following code attempts to extract a symbol name from a string:
extensionStart = int(filename.rfind('.'))
filenameStart = int(filename.rfind('/'))
#print 'Extension Start - ' + str(extensionStart)
#print 'FileName Start - ' + str(filenameStart)
currentSymbol=filename[int(filenameStart),int(extensionStart)]
Uncommenting the print statements clearly show the values to be
integers (and without the str casts actually provide int+string
errors)
However, executing this code results in...
opening - /Users/rmac/Documents/Sandbox/data/MarketData/AA.csv
Traceback (most recent call last):
File rHistFileToDB_Equities.py, line 25, in module
currentSymbol=filename[int(filenameStart),int(extensionStart)]
TypeError: string indices must be integers
You are using , inside filename[]. The splicing syntax is start:end, not
start,end.
You are better off with using the appropriate APIs from the os.path module.
http://docs.python.org/lib/module-os.path.html
import os.path
filename = os.path.basename(path)
prefix, extension = os.path.splitext(filename)
Christian
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Re: Python newbie question re Strings and integers
currentSymbol=filename[int(filenameStart),int(extensionStart)] Should be currentSymbol=filename[int(filenameStart):int(extensionStart)] (change , to :) You don't need to convert to int all the time, rfind will return an integer. Also you can use os.path for this from os.path import basename, splitext currentSymbol = splitext(basename(filename))[0] HTH, -- Miki [EMAIL PROTECTED] http://pythonwise.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Python newbie question re Strings and integers
Ah! Arghh!!! You are so correct on the usage of the ':' Python syntax is a little different from what I am used to. Thank you. -- http://mail.python.org/mailman/listinfo/python-list
