As somebody who is new to C++ and coming from a python background, I am trying to translate the code below to C++
f = open('transit_test.py')
s = f.read()
What is the shortest C++ idiom to do something like this?
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3you're just trying to showoff! :/JohnB– JohnB2010-07-20 03:45:33 +00:00Commented Jul 20, 2010 at 3:45
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1@JohnB: Or looking for sympathy?Dan Breslau– Dan Breslau2010-07-20 04:01:01 +00:00Commented Jul 20, 2010 at 4:01
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1I don't think reading a file is "showing off".Joey Adams– Joey Adams2010-07-20 04:33:17 +00:00Commented Jul 20, 2010 at 4:33
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3 Answers
The C++ STL way to do this is this:
#include <string>
#include <iterator>
#include <fstream>
using namespace std;
wifstream f(L"transit_test.py");
wstring s(istreambuf_iterator<wchar_t>(f), (istreambuf_iterator<wchar_t>()) );
3 Comments
Don Reba
Yes, it will. Unfortunately, STL does not provide an automatic way of loading files in arbitrary encodings, so you either need to know the encoding of the file in advance and adjust the code accordingly or use a library to recognize the encoding and perform the appropriate conversion.
Abyx
R s(T(f), T()); is a function declaration.
DevSolar
@Abyx:
R s(T(f), (T()) ); isn't. ;)I'm pretty sure I've posted this before, but it's sufficiently short it's probably not worth finding the previous answer:
std::ifstream in("transit_test.py");
std::stringstream buffer;
buffer << in.rdbuf();
Now buffer.str() is an std::string holding the contents of transit_test.py.
2 Comments
Loki Astari
Does that not cause a redundant copy? How about this. stackoverflow.com/questions/132358/…
Jerry Coffin
@Martin: It does, but unless I encountered a real problem from it (which I haven't yet), I'd tend to wonder whether attempting to avoid it wasn't a premature optimization.
You can do file read in C++ as like,
#include <iostream>
#include <fstream>
#include <string>
int main ()
{
string line;
ifstream in("transit_test.py"); //open file handler
if(in.is_open()) //check if file open
{
while (!in.eof() ) //until the end of file
{
getline(in,line); //read each line
// do something with the line
}
in.close(); //close file handler
}
else
{
cout << "Can not open file" << endl;
}
return 0;
}
2 Comments
Jerry Coffin
Along with being relatively long, this is buggy: it'll typically appear to read the last line twice (
while (!in.eof()) is pretty much a guaranteed bug).Loki Astari
Never put the test for eof in the while condition.