I am getting some large logs from a several sources and appending them to a list. All of the list values have several \n characters.
Once the list has been populated with the logs I require, I want to output them to a file in $HOME like so:
def logfile_creation(self):
with open(os.path.join(self.homedir, self.logfile), 'w') as logoutput:
for output in self.logs:
logoutput.writelines(str(output))
When I read the logoutput file, instead of a newline the \n character is printed. I assume this is occurring because each list value is being converted into a string with str(), however this seems required for writelines to output into the file.
What's the best way to process the newline as it's outputted into the file, rather than printing \n?
In case anyone was wondering, the way I resolved this was to use:
logoutput.writelines(str(output).replace('\n', '\n'))
Easy as that :)
Related
I am keeping a large repository of strings in a character-delimited file. Currently, I am reading the strings into string variables, and then later printing them.
The problem I'm facing is how to store and print new line characters. In the file, if the string, for example, is:
"Hello this is \n\n a new line"
then the literal '\n' is printed in my program terminal when I print the string, however I would like to print new lines.
Is this a matter of processing the strings character by character, or is there a proper way to read the strings into the string variables that will allow this to work?
I am using boost::property_tree to read and write xml configuration files. I want to change the value of some tags in my code and write them back to file, with some reasonable xml formatting (new lines, indenting, etc.).
Currently I am using
std::fstream fs("filename");
boost::property_tree::ptree pt;
bpt::xml_parser::read_xml(fs,pt);
// replace value
pt.erase("tagname");
pt.put("tagname",newval);
bpt::xml_parser::xml_writer_settings<char> xmlstyle(' ',4);
bpt::xml_parser::write_xml("filename",pt,std::locale(),xmlstyle);
But it seems that every time a tag is deleted, it leaves behind a blank line and after some iterations the xml becomes unreadable. Is there a way to remove empty lines from the property tree itself or from the resulting xml file using boost?
I know there are other ways of removing the newlines by reading and parsing the entire file again, but I was hoping for a more convenient one-liner.
Ok, it looks like the answer was already out there on Stack Overflow, I just hadn't found it (newlines were not mentioned in the post)
boost::property_tree XML pretty printing
The solution is to read the file with boost::property_tree::xml_parser::trim_whitespace
Not Boost, but blank lines in particular.
You can use std::regex_replace() on the output before it is written to the file, removing the blank lines, like this
std::regex_replace(std::ostreambuf_iterator<char>(fout), text.begin(), text.end(), std::regex("(\\n+)"), "\n");
With fout as the file output stream and text as the output data as a std::string.
This replaces every newline followed by another newline w/o any characters in between with a single newline.
I tried it but it comes in the form of a list in the file. I want it in a format without the brackets and the commas.
Let's start by the long way, to make it clear:
for item in mylist:
f.write(str(item) + " ")
The above code will write your items (not necessarily strings, that's why the str() is applied) separated by spaces.
You can achieve the same thing without a loop, using the string's join() method, which takes a list of strings and joins them using the spaces, like this:
f.write(' '.join(map(str, mylist)))
files have a writelines method. use that instead of write
ifstream file;
file.open("file.csv");
string str;
while(file.good())
{
getline(file,str,',')
if (___) // string was split from delimiter
{
[do this]
}
else // string was split from eol
{
[do that]
}
}
file.close();
I'd like to read from a csv file, and differentiate between what happens when a string is split off due to a new line and what happens when it is split off due to the desired delimiter -- i.e. filling in the ___ in the sample code above.
The approaches I can think of are:
(1) manually adding a character to the end of each line in the original file,
(2) automatically adding a character to the end of each line by writing to another file,
(3) using getline without the delimiter and then making a function to split the resulting string by ','.
But is there a simpler or direct solution?
(I see that similar questions have been asked before, but I didn't see any solutions.)
My preference for clarity of the code would be to use your option 3) - use getline() with the standard '\n' delimiter to read the file into a buffer line by line and then use a tokenizer like strtok() (if you want to work on the C level) or boost::tokenizer to parse the string you read from the file.
You're really dealing with two distinct steps here, first read the line into the buffer, then take the buffer apart to extract the components you're after. Your code should reflect that and by doing so, you're also avoiding having to deal with odd states like the ones you describe where you end up having to do additional parsing anyway.
There is no easy way to determine "which delimiter terminated the string", and it gets "consumed" by getline, so it's lost to you.
Read the line, and parse split on commas yourself. You can use std::string::find() to find commas - however, if your file contains strings that in themselves contain commas, you will have to parse the string character by character, since you need to distinguish between commas in quoted text and commas in unquoted text.
Your big problem is your code does not do what you think it does.
getline with a delimiter treats \n as just another character from my reading of the docs. It does not split on both the delimiter and newline.
The efficient way to do this is to write your oen custom splitting getline: cppreference has a pretty clear description of what getline does, mimicing it should be easy (and safer than shooting from the hip, files are tricky).
Then return both the string, and information about why you finished your parse in a second channel.
Now, using getline naively then splitting is also viable, and will be much faster to write, snd probably less error prone to boot.
I have an issue with a file I am trying to read in and I don't know how to do solve it.
The file is a CSV, but there are also commas in the text of the file, so there are quotes around the commas indicating new values.
For instance:
"1","hello, ""world""","and then this" // In text " is written as ""
I would like to know how to deal quotes using a QFileStream (though I haven't seen a base solution either).
Furthermore, another problem is that I also can't read line by line as within these quotes there might be newlines.
In R, there is an option of quotes="" which solves these problems.
There must be something in C++. What is it?
You can split by quote (not just quote, but any symbol, like '\' for example) symbol in qt, just put \ before it, Example : string.split("\""); will split string by '"' symbol.
Here is a simple console app to split your file (the easiest solution is to split by "," symbols seems so far):
// opening file split.csv, in this case in the project folder
QFile file("split.csv");
file.open(QIODevice::ReadOnly);
// flushing out all of it's contents to stdout, just for testing
std::cout<<QString(file.readAll()).toStdString()<<std::endl;
// reseting file to read again
file.reset();
// reading all file to QByteArray, passing it to QString consructor,
// splitting that string by "," string and putting it to QStringList list
// where every element of a list is value from cell in csv file
QStringList list=QString(file.readAll()).split("\",\"",QString::SkipEmptyParts);
// adding back quotes, that was taken away by split
for (int i=0; i<list.size();i++){
if (i!=0) list[i].prepend("\"");
if (i!=(list.size()-1)) list[i].append("\"");
}//*/
// flushing results to stdout
foreach (QString i,list) std::cout<<i.toStdString()<<std::endl; // not using QDebug, becouse it will add more quotes to output, which is already confusing enough
where split.csv contains "1","hello, ""world""","and then this" and the output is:
"1"
"hello, ""world"""
"and then this"
After googling I've found some ready solution. See this article about qxt.