Hey so I haven't really messed around with it too much, but I was wondering if there was actually a way (before I go down a neverending rabbit hole) to read and write to CSV files in Dart/Flutter? I need to write to the files, not necessarily read them, and I'm willing to go to quite extreme lengths to do so. Any library works, built-in functions are even better. Any and all help is appreciated!
Use package csv from https://pub.dartlang.org/packages/csv
If you have a List<List<dynamic>> items that needs to convert into csv,
String csv = const ListToCsvConverter().convert(yourListOfLists);
If you want to write the csv to a file,
/// Write to a file
final directory = await getApplicationDocumentsDirectory();
final pathOfTheFileToWrite = directory.path + "/myCsvFile.csv";
File file = await File(pathOfTheFileToWrite);
file.writeAsString(csv);
Also, if you want to read a csv file directly into list<list<dynamic>>
final input = new File('a/csv/file.txt').openRead();
final fields = await input.transform(UTF8.decoder).transform(csvCodec.decoder).toList();
According to new packages and guidelines(2019) use following code
package csvfrom https://pub.dartlang.org/packages/csv.
If you have a List<List<dynamic>> items that needs to convert into csv,
String csv = const ListToCsvConverter().convert(yourListOfLists);
Then you can write the string to a file using file operations.
file.writeAsString('$csv');
Also, if you want to read a csv file directly into list<list<dynamic>>
final input = new File('a/csv/file.txt').openRead();
final fields = await input.transform(utf8.decoder).transform(new CsvToListConverter()).toList();
Related
I want to convert the following line of a file into JSON, I want to save that into an mongoose schema.
>HWI-ST700660_96:2:1101:1455:2154#5#0/1
GAA…..GAATG
Should be:
{“>HWI-ST700660_96:2:1101:1455:2154#5#0/1”: “GAA…..GAATG”}
I have tried several options, one sample below, but no success, any suggestion?
const parser = require("csv-parse/lib/sync");//import parser
const fs = require("fs");//import file reader
const path = require("path");//for join paths
const sourceData = fs.readFileSync(path.join(__dirname, "Reads.txt"), "utf8");//read the file, locally stored
console.log(sourceData);//print out for checking
const documents = parser(sourceData);//parsing, it works for other situations I have tested, in a column like data
console.log(documents);//printing out
This code give me an output as following:
[ [ '>HWI-ST700660_96:2:1101:1455:2154#5#0/1' ],
[ 'GAATGGAATGAAATGGATAGGAATGGAATGGAATGGAATGGATTGGAATGGATTAGAATGGATTGGAATGGAATGAAATTAATTTGATTGGAATGGAATG' ],...
Similar question: fasta file reading python
Because you are using the default config of the parser, it does simply output arrays of arrays in that configuration.
If you want to receive objects you will need to give the parser some options (columns) first. Take a look at the doc.
When using the sync parsing mode (like you are using) you can provide options like this:
const documents = parse(sourceData, {columns: true})
columns:true will infer the column names from the first line of the input csv.
So im making this memory game and im trying to add a scoreboard and i want to write the data to a txt file using JSON. I got all of that to work but now i have a small issue, everytime i run my program the existing data in my txt file gets overwritten by the new data.
Here is the code that i use:
public static void Score(String gamescore, string loginname)
{
List<Highscore> Myhighscores = new List<Highscore>();
Myhighscores.Add(new Highscore { Score = gamescore, Name = loginname });
string Jstr = JsonConvert.SerializeObject(Myhighscores);
File.WriteAllText(#"c:\temp\hs.txt", Jstr);
}
does anyone know how i can keep the existing data and also write the new data into the txt file?
I figured it out my self all i needed to do is read the existing data like this:
string hs = File.ReadAllText(#"c:\temp\hs.txt");
and put it back into my list "Myhighscores" like this:
Myhighscores = JsonConvert.DeserializeObject<List<Highscore>>(hs);
No thanks to Sagar V who just bitched that i put the jquery tag in.
I am importing .CSV file from an angular app into MVC and i am able to get the files like this
Int32 strLen, strRead;
System.IO.Stream stream = Request.InputStream;
strLen = Convert.ToInt32(stream.Length);
byte[] strArr = new byte[strLen];
strRead = stream.Read(strArr, 0, strLen);
here the files which is being imported is converted into byte[] because i am reading the file using
System.IO.Stream stream = Request.InputStream
Then i convert it into string like this
string a = System.Text.Encoding.UTF8.GetString(strArr);
and try to split the content and retrieve the data but it becomes very complex, i wonder if there is any alternate way for it. In a simple .CSV file like this
I get the result after converting the byte[] to string like this
and once i apply logic for splitting the string and retrieving the data, the logic gets very messy like this
Is there any efficinet way where i can convert the imported .CSV file to JSON
Save stream as text file in to the TEMP folder.
Use any parcer for working with CSV file. (Example FileHelpers)
Use any Json helper to convert it to the output format. (Example: newtonsoft)
You can use Cinchoo ETL - an open source library, to convert CSV to JSON easily.
using (var parser = new ChoCSVReader("IgnoreLineFile1.csv")
.WithField("PolicyNumber", 1)
.WithField("VinNumber", 2)
.Configure(c => c.IgnoreEmptyLine = true)
.Configure(c => c.ColumnCountStrict = true)
)
{
using (var writer = new ChoJSONWriter("ignoreLineFile1.json")
.WithField("PolicyNumber", fieldName: "Policy Number")
.WithField("VinNumber", fieldName: "Vin Number")
)
writer.Write(parser.Skip(1));
}
In above, you can pass stream to the reader and writer as well for your requirement.
Hope this will help.
Disclaimer: I'm the author of this library.
I am working with Flink streaming API and I want to continuously read CSV files from a folder, ignore the header and convert each row in the CSV file into a Java class (POJO). After all this processing, I should obtain a stream of Java objects(POJOs).
So far, I do the following to partially achieve the behavior(code below):
read the CSV files as regular text files, continuously
get a stream of strings from the CSV files
convert the stream of strings to a stream of Java objects
String path = "/home/cosmin/Projects/flink_projects/flink-java-project/data/";
TextInputFormat format = new TextInputFormat(
new org.apache.flink.core.fs.Path(path));
DataStream<String> inputStream = streamEnv.readFile(format, path, FileProcessingMode.PROCESS_CONTINUOUSLY, 100);
DataStream<MyEvent> parsedStream = inputStream
.map((line) -> {
String[] cells = line.split(",");
MyEvent event = new MyEvent(cells[1], cells[2], cells[3]);
return event;
});
However, with this I don't manage to remove the header line in each CSV file.
I have read that I can build a custom connector for reading CSV files by using createInput() or addSource () methods on the StreamExecutionEnvironment class.
Can you help with some guidance on how to achieve this, as I haven't found any examples beyond the Javadoc?
You could chain a filter function before your map function to filter out header lines
inputStream.filter(new FilterFunction<String>() {
public boolean filter(String line) {
if (line.contains("some header identifier")) return false;
else return true;
}
}).map(...) <Your map function as before>
I have created an application in which I am inserting data to the file. It is working fine. Following is my code:
private async void btnSearch_Click(object sender, RoutedEventArgs e)
{
UserDetails details = new UserDetails
{
Name= TxtName.Text,
Course= TxtCouse.Text,
City=TxtCity.Text
};
string jsonContents = JsonConvert.SerializeObject(details);
StorageFolder localFolder = await ApplicationData.Current.LocalFolder.CreateFolderAsync("Storage", CreationCollisionOption.ReplaceExisting); ;
StorageFile textFile = await localFolder.CreateFileAsync("UserDetails.txt", CreationCollisionOption.ReplaceExisting);
using (IRandomAccessStream textStream = await textFile.OpenAsync(FileAccessMode.ReadWrite))
{
// write the JSON string!
using (DataWriter textWriter = new DataWriter(textStream))
{
textWriter.WriteString(jsonContents);
await textWriter.StoreAsync();
}
}
this.Frame.Navigate(typeof(BlankPage1));
}
Now I want that, when a user enter new data the data will append to the same existing file.
Appending data to a JSON text file would mean doing some parsing of the file to find the correct location to insert the text. That is, because JSON is structured with {} delimiters, it's not a simple matter of just appending text to the end of the file.
Given that your data doesn't look that large, the easiest thing to do is to deserialize the JSON from the existing file into memory, add your additional properties to that data structure, and then serialize back to JSON. In that case you probably just want to maintain the structure in memory during the app session, and just overwrite the file with new data whenever you need to. But of course you could also reopen the file, read/parse the JSON into memory, and then rewrite the contents.