I don't quite have an answer but I'm narrowing it down. Somehow I'm mixing/confusing types, I believe, between what is provided by commands like 'os.path' and type str().
As I've made the assignment of the logfile(s) globally, even though I can print it in the function, when the variable is used in fout = open(... it's actually a null that's being referenced, i.e. open() doesn't like/can't use the type it finds.
The error:
UnboundLocalError: local variable 'fout' referenced before assignment
I am simply writing a log of dot files (left on USB drives by OSX) for deletion, but the try/except is now falling over. First the original version.
working code:
logFile = "/Users/dee/Desktop/dotFile_names.txt"
try:
fout = open(logFile, 'w')
for line in dotFile_names:
fout.write(line)
except IOError as e:
print ("Error : %s not found." % fout)
finally:
fout.close()
Attempting better practice, I sought to put the log file specs and path as variables so they can be modified if need be - I hope to make it cross platform workable. these variables are at the head of the program, i.e. not in main(), but I pass them in and print() statements have shown me they are successfully being referenced. i.e. I get this printed:
/Users/dee/Desktop/dotFile_names.txt
Despite this the error I get is:
UnboundLocalError: local variable 'fout' referenced before assignment -
error points at the "fout.close()" line
Error producing code
logFilespec = "dotFile_names.txt"
fullLogFileSpec = []
userDesktop = os.path.join(os.path.expanduser('~'), 'Desktop')
fullLogFilespec = os.path.join(userDesktop, logFilespec)
try:
print "opening " + fullLogFilespec
fout = open(fullLogFileSpec, 'w')
for line in dotFile_names:
print "..", # are we executing this line..?
fout.write(line)
except IOError as e:
print ("Error : %s not found." % fout)
finally:
print "\nclosing " + fullLogFilespec
fout.close()
I've found that if I modify this line by converting to a string
fout = open(fullLogFileSpec, 'w')
fout = open(str(fullLogFileSpec), 'w')
the error goes away, BUT NO file is created on the Desktop!
At the very least I guess that I am passing something unrecognisable to fout = open() but it is not being caught by the except. Then when I pass something that does seem to allow fout =open() to work it seems to be a ghost?
So I figure I am lost between a String and whatever kind of reference/pointer os.path.expanduser() gives me.
I'm sure it's insanely simple. Before adding the str() code I also checked all indentation, removing them all and adding back using the editor indent hotkeys, just in case that was affecting things somehow.
OK, it looks like I was wearing my dumb glasses, I think declaring
fullLogFileSpec = []
as a list instead of a string was my error.
Similar as it is, having re-written it without that list declaration this code is working fine:
logfile_directory = os.path.join(os.path.expanduser('~'),'Desktop')
log_bf_file_spec = 'ItemsFoundByFolder_' + Deez_1.current_datetime() + '.txt'
log_by_folder = os.path.join(logfile_directory, log_bf_file_spec)
the function later calls, with no error:
fout_by_folder = open(log_by_folder, 'w')
Related
Is there a way to have IPython open a browser pointed at the appropriate online reference?
Especially for numpy,scipy, matplotlib?
For example, the doc for numpy.linalg.cholesky is pretty hard to read in a terminal.
I don't think there is a direct way to make IPython or any shell to open up documentation online, because the primary job of shells is to let you interact with the things they are shells to.
We could however write a script to open a new tab on a browser with the documentation. Like so:
import webbrowser
docsList = {
"numpy" : lambda x: "https://docs.scipy.org/doc/numpy/reference/generated/" + x + ".html",
"scipy" : lambda x: "https://docs.scipy.org/doc/scipy/reference/generated/" + x + ".html",
"matplotlib" : lambda x: "https://matplotlib.org/api/" + x.split('.')[1] + "_api.html",
"default" : lambda x: "https://www.google.com/search?q=documentation+" + x
}
def online(method_name):
"""
Opens up the documentation for method_name on the default browser.
If the package doesn't match any entry in the dictionary, falls back to
Google.
Usage
-------
>>> lookUp.online("numpy.linalg.cholesky")
>>> lookUp.online("matplotlib.contour")
"""
try:
url = make_url(method_name)
except AttributeError:
print("Enter the method name as a string and try again")
return
webbrowser.open(url, new = 2)
return
def make_url(method_name):
package_name = method_name.split('.')[0]
try:
return docsList[package_name](method_name)
except KeyError:
return docsList["default"](method_name)
You could save the above as "lookUp.py" at a location that Python can find it in, and then import it whenever you need to use it.
Caveats:
This method takes strings as input, so if you call it on a function it'll throw an error.
>>> lookUp.online("numpy.linalg.cholesky")
Will work.
>>> lookUp.online(numpy.linalg.cholesky)
Will ask you to give it as a string.
So use autocomplete to get to the function and then wrap it in quotes to get it to work.
First time user, looking for help with a script that's been driving me crazy.
Basically, I need to create a set number of files of an exact size (512KB, 2MB, 1GB) to test a SAN. These files need to be filled with random text so that the SAN doesn't catch the nuls and does actually allocate the blocks - that's also the reason I couldn't just use fsutils.
Now, I've been messing with the new-bigrandomfile by Verboon and tweaking it to my needs.
However I'm getting the error:
You cannot call a method on a null-valued expression.
At L:\random5.ps1:34 char:9
+ $stream.Write($longstring)
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (:) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
This is the bit of code I've come up with so far; I'll add a loop at the end to copy the file I just created N times so to fill up the lun.
Set-Strictmode -Version 2.0
#temp file
$file = "c:\temp\temp.rnd"
#charset size
$charset = 64
#Block Size
$blocksize = 512
#page size
$Pagesize = 512KB
#Number of blocks in a page
$blocknum = $Pagesize / $blocksize
#Resulting/desired test file size
$filesize = 1GB
#number of pages in a file
$pagenum = $filesize / $Pagesize
# create the stream writer
$stream = System.IO.StreamWriter $file
# get a 64 element Char[]; I added the - and _ to have 64 chars
[char[]]$chars = 'azertyuiopqsdfghjklmwxcvbnAZERTYUIOPQSDFGHJKLMWXCVBN0123456789-_'
1..$Pagenum | ForEach-Object {
# get a page's worth of blocks
1..$blocknum| ForEach-Object {
# randomize all chars and...
$rndChars = $chars | Get-Random -Count $chars.Count
# ...join them in a string
$string = -join $rndChars
# repeat random string N times to get a full block string length
$longstring = $string * ($blocksize / $charset)
# write 1 block to file
$stream.Write($longstring)
# release resources by clearing string variables
Clear-Variable string, longstring
}
}
$stream.Close()
$stream.Dispose()
# release resources through garbage collection
[GC]::Collect()
$file.Close()
I've tried a gazillion variants like:
$stream = [System.IO.StreamWriter] $file
$stream = System.IO.StreamWriter $file
$stream = NewObject System.IO.StreamWriter $file
Of course, being a total noob at powershell, I've tried using quotes, brackets, provided the full path instead of the variable, etc. All (or most) seem to be valid syntax variants, according to a ton of examples I found online, but the output is still the same.
In case you have any improvement to suggest or alternative way to perform this task I'm all ears.
Edited the script above: just a couple of " for $file made the error disappear, - thanks LinuxDisciple; however, the file gets created but stays at 0 bytes and the script stuck in a loop.
Fix your instantiation of StreamWriter to any of these correct variants:
$stream = [System.IO.StreamWriter]::new($file)
$stream = [IO.StreamWriter]::new($file) # the default namespace may be omitted
$stream = New-Object System.IO.StreamWriter $file
You can specify encoding:
$stream = [IO.StreamWriter]::new(
$file,
$false, # don't append
[Text.Encoding]::ASCII
)
See StreamWriter on MSDN for available constructors and parameters.
PowerShell ISE offers autocomplete with tooltips:
type [streamw and press Ctrl-Space to autocomplete the full .NET class name
type ]:: to see the available methods and properties
type new and press Ctrl-Space to see the constructor overrides
whenever needed, put the caret at the method name and press Ctrl-Space for the tooltip
I know nothing about powershell but a few things:
Are you sure $longstring has a value before you call stream.Write()? It sounds like it's null and that's why the error. If you can somehow output the value of $longstring to the console, it would help you make sure that it has a value.
Also, troubleshoot the code with a simplified version of your code, so that you can pinpoint what's going on, for example
$file = c:\temp\temp.rnd
$stream = System.IO.StreamWriter $file
$longstring = 'whatever'
$stream.Write($longstring)
I'm writing an LPeg-based parser. How can I make it so a parsing error returns nil, errmsg?
I know I can use error(), but as far as I know that creates a normal error, not nil, errmsg.
The code is pretty long, but the relevant part is this:
local eof = lpeg.P(-1)
local nl = (lpeg.P "\r")^-1 * lpeg.P "\n" + lpeg.P "\\n" + eof -- \r for winblows compat
local nlnoeof = (lpeg.P "\r")^-1 * lpeg.P "\n" + lpeg.P "\\n"
local ws = lpeg.S(" \t")
local inlineComment = lpeg.P("`") * (1 - (lpeg.S("`") + nl * nl)) ^ 0 * lpeg.P("`")
local wsc = ws + inlineComment -- comments count as whitespace
local backslashEscaped
= lpeg.P("\\ ") / " " -- escaped spaces
+ lpeg.P("\\\\") / "\\" -- escaped escape character
+ lpeg.P("\\#") / "#"
+ lpeg.P("\\>") / ">"
+ lpeg.P("\\`") / "`"
+ lpeg.P("\\n") -- \\n newlines count as backslash escaped
+ lpeg.P("\\") * lpeg.P(function(_, i)
error("Unknown backslash escape at position " .. i) -- this error() is what I wanna get rid of.
end)
local Line = lpeg.C((wsc + (backslashEscaped + 1 - nl))^0) / function(x) return x end * nl * lpeg.Cp()
I want Line:match(...) to return nil, errmsg when there's an invalid escape.
LPeg itself doesn't provide specific functions to help you with error reporting. A quick fix to your problem would be to make a protected call (pcall) to match like this:
local function parse(text)
local ok, result = pcall(function () return Line:match(text) end)
if ok then
return result
else
-- `result` will contain the error thrown. If it is a string
-- Lua will add additional information to it (filename and line number).
-- If you do not want this, throw a table instead like `{ msg = "error" }`
-- and access the message using `result.msg`
return nil, result
end
end
However, this will also catch any other error, which you probably don't want. A better solution would be to use LPegLabel instead. LPegLabel is an extension of LPeg that adds support for labeled failures. Just replace require"lpeg" with require"lpeglabel" and then use lpeg.T(L) to throw labels where L is an integer from 1-255 (0 is used for regular PEG failures).
local unknown_escape = 1
local backslashEscaped = ... + lpeg.P("\\") * lpeg.T(unknown_escape)
Now Line:match(...) will return nil, label, suffix if there is a label thrown (suffix is the remaining unprocessed input, which you can use to compute for the error position via its length). With this, you can print out the appropriate error message based on the label. For more complex grammars, you would probably want a more systematic way of mapping the error labels and messages. Please check the documentation found in the readme of the LPegLabel repository to see examples of how one may do so.
LPegLabel also allows you to catch the labels in the grammar by the way (via labeled choice); this is useful for implementing things like error recovery. For more information on labeled failures and examples, please check the documentation.
So this is my function which is meant to read the lines of text from a file.
This is extracted from a larger program hence some of the comments may seem out of place. Anyways I need to use the functions text and file_lines in numerous other functions but even after declaring them as global I still get the UnboundLocalError: local variable 'file_lines' referenced before assignment error and I don't know what to do.
import sys
text = []
case = ''
file_lines = []
def read_file(file): # function to read a file and split it into lines
global text #sets variable text as a global variable for use in multiple locations
global case #handles case sensitivity.
try: #tests the statement after colon
open(file)
except:
print('oops no file found bearing that name')
else:
while file == '': #if the file name is blank print error, this prevents program from crashing
print ('error')
filename = input('enter a file and its extension ie file.ext\n>>')
with open(file) as f : #opens filewith name
text = f.read() #read all lines of program text.
print ("file successfully read")
print('TEXT SENSITIVITY TURNED ON !!!!!!')
text = text.split('\n')# breaks lines in file into list instead of using ".readlines"
# so that the program doesn't count blank lines
case == True
global file_lines
file_lines = text
a function that tries to use the read_lines variable would be
def find_words(words):
line_num = 0 # to count the line number
number_of_word = 0
if case == False:
words = words.lower()
file_lines = [file_lines.lower() for file_lines in text]
while "" in file_lines:
file_lines.remove('')
for lines in file_lines:
line_num += 1
if words in lines: #checks each for the words being looks for
print(line_num,"...", text[line_num-1])
number_of_word = 1
if number_of_word == 0: #to check if the word is located in the file
print('Words not found')
In your function find_words you forgot to specify that find_lines is global. Try
def find_words(words):
global file_lines
line_num = 0 # to count the line number
The function errors because file_lines is not defined within the scope of find_words otherwise.
Situation :
There are two sensors and I want to save the data of values of each sensor in the certain file..But it's not working. I am working on linux system and the file is still empty.
What's wrong with my code? any suggestion please?
my code is:
--Header file
require("TIMER")
require("TIMESTAMP")
require("ANALOG_IN")
function OnExit()
print("Exit code...do something")
end
function main()
timer = "TIMER"
local analogsensor_1 = "AIR_1"
local analogsensor_2 = "AIR_2"
local timestr = os.data("%Y-%m-%d %H:%M:%S")
-- open the file for writing binary data
local filehandle = io.open("collection_of_data.txt", "a")
while true do
valueOfSensor_1 = ANALOG_IN.readAnalogIn(analogsensor_1);
valueOfSensor_2 = ANALOG_IN.readAnalogIn(analogsensor_2);
if (valueOfSensor_1 > 0 and valueOfSensor_2 > 0) then
-- save values of sensors
filehandle:write(timestr, " -The Value of the Sensors: ", tostring(valueOfSensor_1), tostring(valueOfSensor_2)"\n");
end
TIMER.sleep(timer,500)
end
-- close the file
filehandle:close()
end
print("start main")
main()
I do not know what this libs realy do.
But this code is incorrect;
1) you do not close while statement.
if in real code you close it before filehandle:close() then try call filehandle:flush()
2) you forgot comma:
filehandle:write(timestr, " -The Value of the Sensors: ", tostring(valueOfSensor_1), tostring(valueOfSensor_2)"\n")
(it should seay something like attemt call a number value).
3) try print out valueOfSensor_1 and valueOfSensor_2 values. May be there no data.
Beside the typos pointed out by #moteus, shouldn't this:
if (valueOfSensor_1 and valueOfSensor_2 > 0) then
be like this?
if (valueOfSensor_1 > 0 and valueOfSensor_2 > 0) then
Edit, in response to your comment to another answer:
still error..it says "attempt to call field 'data' (a nil value)
I can't be sure without the stack trace, but, most likely, something bad happens in the ANALOG_IN library code. You may not be using it properly.
try to turn this:
valueOfSensor_1 = ANALOG_IN.readAnalogIn(analogsensor_1);
valueOfSensor_2 = ANALOG_IN.readAnalogIn(analogsensor_2);
into this:
success, valueOfSensor_1 = pcall(ANALOG_IN.readAnalogIn, analogsensor_1);
if not success then
print("Warning: error reading the value of sensor 1:\n"..valueOfSensor_1)
valueOfSensor_1 = 0
end
success, valueOfSensor_2 = pcall(ANALOG_IN.readAnalogIn, analogsensor_2);
if not success then
print("Warning: error reading the value of sensor 2:\n"..valueOfSensor_2)
valueOfSensor_2 = 0
end
If the failure in ANALOG_IN is not systematic, it will work around it. If the call fails systematically, you'll get a huge warning log, and an empty collection_of_data.txt.
Please note that ANALOG_IN is not a standard Lua library. You should check its documentation , and pay attention to the details of its usage.