File in python #3 : Write CSV file, Read and Write JSON file

Repository

https://github.com/python

What Will I Learn?

Write CSV file
Read and Write JSON file

Requirements

Basic Python
Install Python 3
Install Flask

Resources

Difficulty

Basic

Tutorial Content

This tutorial is still related to my previous tutorial about files in python, in the previous tutorial I discussed how to read data with the extension .csv, for those of you who are not at all familiar with python. I suggest you follow my previous tutorial which is in the curriculum section. In this tutorial, I will discuss how to write files with extension .csv using python and not only that we will also intersect with data formats that we use very often, namely JSON. For that, we just start this tutorial.

Write CSV file

What we will learn first is how to write a CSV file, please note that the .csv file is a form of a file that is separated by commas(,). The comma in the CSV file can be interpreted as a column. We can look at the picture below, to illustrate what I call a column:

Set Column

We will begin our first task, which is writing a column in the CSV file. For methods when opening files we will use the method 'a', keep in mind this method is used so that when we write a file, we do not replace the previous value. for more details, we can see the code below:

csvwriter.py

import csv

## Write
with open('writeData.csv', 'a') as filecsv:
    fields = ['Name', 'Lastname', 'age']
    writer = csv.DictWriter(filecsv, fieldnames = fields)

Like the code we see above, we must have a reference column as a key to determine the column length of the CSV file that we wrote. The tutorial above we use 3 key columns, They are fields = ['Name', 'Lastname', 'age'].
After defining the key from the reference column. then we can write the column using the DictWriter() method. by using this method, We write CSV data in the form of dictionary. This function has two mandatory parameters, the first is the file to be written and the second parameter is the key pair and the value of the fields to be written in CSV. We can write it like this code csv.DictWriter(filecsv, fieldnames = fields), fieldsname is the default key of the DictWriter function, so you cannot change it and fields are the values of the column to be written.
Write Column

We have defined the column and key that we will use, well then we will write a dictionary based on the column defined earlier. for more details, we can see the code below:

csvwriter.py

import csv

## Write

rows = [
    {'Name' : 'Millea', 'Lastname': 'Duski', 'Age' : 23},
    {'Name' : 'Sathosi', 'Lastname': 'Nakamoto', 'Age' : 33},
    {'Name' : 'Jhon', 'Lastname': 'Doe', 'Age' : 37},
]
with open('writeData.csv', 'a') as filecsv:
    fields = ['Name', 'Lastname', 'Age']
    writer = csv.DictWriter(filecsv, fieldnames = fields)

    writer.writeheader()
    writer.writerows(rows)

writeheader() used to write headers from CSV or key columns that are referenced from the next row.
writerows(rows) used to write rows that refer to the header. This function requires a parameter containing the key and value from the reference column and a new row. We create a variable to store new rows, they are in objects. in this tutorial it is defined as the data below:

rows = [
    {'Name' : 'Millea', 'Lastname': 'Duski', 'Age' : 23},
    {'Name' : 'Sathosi', 'Lastname': 'Nakamoto', 'Age' : 33},
    {'Name' : 'Jhon', 'Lastname': 'Doe', 'Age' : 37},
]

The 'Name' is the name of the reference we have defined in the previous section and 'Millea' is the value of the new row. After that, we can run our programme and we can see the results as shown below:

ezgif.com-video-to-gif (2).gif

We can see in the picture above before we did not have the writeData.csv file after we run the program automatically the system creates the file writeData.csv, We have successfully written in the CSV file.

Read and Write JSON file

The next lesson is to write and read JSON format. we'll see some differences when we use .csv and .json files. Discussing files, of course, this one file format should not be missed, because this file format is the one we use most often. This data format is often encountered when we intersect with the API. So we just learned how to read and write this format in python.

Write JSON

What I will do first is how to write data in JSON format in the format of txt, to access JSON format data we are assisted with a json module import json that has been built-in python. to write JSON format the method is quite easy, we can see in the code below:

readJSON.py.

import json

 data = {}
 data["member"] = [
    {'Name' : 'Millea', 'Lastname': 'Duski', 'Age' : 23},
    {'Name' : 'Sathosi', 'Lastname': 'Nakamoto', 'Age' : 33},
    {'Name' : 'Jhon', 'Lastname': 'Doe', 'Age' : 37}
 ]

 with open('member.txt', 'w') as filemember:
    json.dump(data, filemember)

We will write the JSON format into the TXT format file, So from then on I will create an object that contains data in JSON format like this:

 data["member"] = [
    {'Name' : 'Millea', 'Lastname': 'Duski', 'Age' : 23},
    {'Name' : 'Sathosi', 'Lastname': 'Nakamoto', 'Age' : 33},
    {'Name' : 'Jhon', 'Lastname': 'Doe', 'Age' : 37}
 ]

I provide key member data["member"] in JSON data. but before we have to define variables with object {} types.

And as we have learned before we use the open() method and the 'w' function to write data and to write JSON data is quite easy by using the dump() method from module json. The dump function has two mandatory parameters, The first is the data to be written and The second alias of the file that is the place to write data.

If it's finished we can see the results as shown below:

ezgif.com-video-to-gif (3).gif

Read JSON

The next part we will learn how to read JSON files, the method is not much different from how to read CSV files. We will read the file that we have created at the top, that is member.txt. The contents of the member.txt file are data with JSON format. For more details, we can see the code as follows

import json

with open('member.txt', 'r') as filemember:
    data = json.load(filemember)

    for member in data["member"]:
        print("The name is :" + member["Name"] + " and the Age is : " + member["Name"])

As we have learned before to do read data we need the 'r' method and to load data in the member.txt file we can use the load () function and pass the alias from the file to its parameters json.load(filemember).
Then we save the data into a variable that we will do looping to see the data inside. We can use for to do looping and that must be remembered , the JSON data that we use is wrapped into one key.the key is "member", so that we will looping it into something like this for member in data["member"]: and we will loop with each key and print it to show the data.

If there is no mistake, we will see the results as follows:

ezgif.com-video-to-gif (4).gif

We can see in the picture above we have succeeded in doing read and write and access to several file formats that we often use in the programming world, I hope you can take lessons from this tutorial, this tutorial is basic, but you can take the information you need this tutorial. Enough to get here, thank you. . .