Use a for loop on a file object to read it line-by-line. Use with open(…) to let a context manager ensure that the file is closed after reading: with open(“log.txt”) as infile: for line in infile: print(line)
The easiest way if the file isn’t too long is: puts File.read(file_name) Indeed, IO.read or File.read automatically close the file, so there is no need to use File.open with a block.
Scanner is used for parsing tokens from the contents of the stream while BufferedReader just reads the stream and does not do any special parsing. In fact you can pass a BufferedReader to a scanner as the source of characters to parse.
mmap is great if you have multiple processes accessing data in a read only fashion from the same file, which is common in the kind of server systems I write. mmap allows all those processes to share the same physical memory pages, saving a lot of memory. mmap also allows the operating system to optimize … Read more
Here’s how you read a file, and then write to it (overwriting any existing data), without closing and reopening: with open(filename, “r+”) as f: data = f.read() f.seek(0) f.write(output) f.truncate()
A CSV parser is now a part of .NET Framework. Add a reference to Microsoft.VisualBasic.dll (works fine in C#, don’t mind the name) using (TextFieldParser parser = new TextFieldParser(@”c:\temp\test.csv”)) { parser.TextFieldType = FieldType.Delimited; parser.SetDelimiters(“,”); while (!parser.EndOfData) { //Process row string[] fields = parser.ReadFields(); foreach (string field in fields) { //TODO: Process field } } } … Read more
Copy a file in a sane way: #include <fstream> int main() { std::ifstream src(“from.ogv”, std::ios::binary); std::ofstream dst(“to.ogv”, std::ios::binary); dst << src.rdbuf(); } This is so simple and intuitive to read it is worth the extra cost. If we were doing it a lot, better to fall back on OS calls to the file system. I … Read more
For reading and writing you should use a location that is writeable, for example documents directory. The following code shows how to read and write a simple string. You can test it on a playground. Swift 3.x – 5.x let file = “file.txt” //this is the file. we will write to and read from it … Read more
To write a lazy function, just use yield: def read_in_chunks(file_object, chunk_size=1024): “””Lazy function (generator) to read a file piece by piece. Default chunk size: 1k.””” while True: data = file_object.read(chunk_size) if not data: break yield data with open(‘really_big_file.dat’) as f: for piece in read_in_chunks(f): process_data(piece) Another option would be to use iter and a helper … Read more
To find the fastest way to read a file line by line you will have to do some benchmarking. I have done some small tests on my computer but you cannot expect that my results apply to your environment. Using StreamReader.ReadLine This is basically your method. For some reason you set the buffer size to … Read more