Working with CSV Files in Julia

17 Jan, 2022
CSV file (Comma-separated values file) is a plain text file that uses commas to separate values and fields. It is majorly used to store data in the form of tables or spreadsheets. Each row of a table or spreadsheet is a record filled with data that belongs to n fields (or Columns). It is used to import or export data and tables very easily and stored with the extension “.csv” in most programming languages.
Julia provides various file handling methods to perform operations on CSV files. These methods can be used to create a CSV file, add contents to the file, Update the File, etc. 
First, you need to Install CSV Package using the following commands on the Julia command line:
using pkg 
pkg.add("Package name")
CSV Package is a built-in package with a defined “N” number of methods to perform n operations.
Julia
# using pkg to install packagesusing Pkg  # using pkg to add csv package file to libraryPkg.add("CSV")
Install Packages
Now you have to Save your data into the CSV file.
Created .csv File
Here we will use the CSV package and read() method in order to read the contents of the CSV File:
Julia
# using Installed csv package for working with csv filesusing CSV # reading the csv fileCSV.read("myfile.csv")
Reading Data from csv file
Here we will learn how to modify the content of an existing file with the help of the write() method in CSV package and DataFrames Package.
Julia
using CSV # using dataframes package to create a dataframeusing DataFrames # Creating DataFrameab = DataFrame(Name = ["AKANKSHA", "TANYA", "PREETIKA", "VRINDA", "JAHNVI"],               Age = [42, 44, 22, 81, 93],               Salary = [540000, 650000, 900000, 770000, 850000],         RESIDENCE=["DELHI", "DELHI", "UP", "HARYANA", "UP"]               )  # modifying the content of myfile.csv using write methodCSV.write("myfile.csv", ab)
Creating a new Dataframe 
Now we will overwrite the existing ‘.csv’ file Using CSV write() method.
Write to existing file
Here we will create a new file using touch() command and therefore use DataFrames and CSV packages to write the newly created dataframe content to a new file.
Julia
# new file createdtouch("newfile.csv") # file handling in write modeefg = open("newfile.csv", "w") # Creating a new dataframemn = DataFrame(Name = ["AKANKSHA", "TANYA", "PREETIKA", "VRINDA", "JAHNVI"],               Age = [42, 44, 22, 81, 93],               Salary = [540000, 650000, 900000, 770000, 850000],         RESIDENCE=["DELHI", "DELHI", "UP", "HARYANA", "UP"]               )                # writing to the newly created fileCSV.write("newfile.csv", mn)
Here we will learn to delete a particular column entry or multiple column entries from a particular table or spreadsheet using the drop command in Julia.
Julia
# Format# CSV.File(filename;drop=["colulm1", "column2"....., column n]) # dropping "RESIDENCE" column from our file (newfile.csv")CSV.File("newfile.csv"; drop=["RESIDENCE"])
Drop column Residence
Here we will learn to query a particular column or set of columns as per demand from the entire table or spreadsheet, and we can even use operators in the query to retrieve a set of rows satisfying the particular condition.
Julia
# Format for select command# CSV.File(file; select=[column1, column2]) # Select the columns 'Name and Salary'CSV.File("newfile.csv"; select=["Name", "Salary"]) # Selecting columns number wise# selecting column 1 and 3CSV.File("newfile.csv"; select=(i, nm) -> i in (1, 3)) # selecting column 1, 2, 3CSV.File("newfile.csv"; select=(i, nm) -> i in (1, 2, 3))
Hence “N” number of operations can be performed on a CSV file in Julia using built-in CSV packages with a pre-defined  “M” number of methods with unique operations.
while using CSV.read(“myfile.csv”), if you find error like “”ArgumentError: provide a valid sink argument””use the below command to solve this error:
Julia
using DataFramesfile = CSV.read("myfile.csv",DataFrames)
mohanapranes
abhishek0719kadiyan
saurabh1990aror
julia-FileHandling
Julia
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