Python – Read CSV file

CSV file reading:

• CSV Stands for “Comma Separated Values”
• CSV is an alternate to MS-Excel sheet
• Text file always stores textual information. It is not recommended to store and process record type information using Text File.
• CSV file stores information in tabular form(Rows and Columns)

Creating data.csv file:

• Open notepad file.
• Write records information by separating with comma
  • 101,amar,5000
  • 102,annie,8000
  • 103,hareen,7500
  • 103,satya,6500
• Save the file with .csv extension
• Close the file and re-open the file.
• File will be opened with MS-Excel software by default.

data.csv file:

Read information of CSV file:

“csv”:

• A pre-defined module belongs to python library.
• It is providing pre-defined functionality to process the information of CSV file.
• Reader() is a method belongs to csv module
• Reader() method returns the CSV file data as an Object to process.

Code:

import csv

class ReadCSV:
    file = None
    def main():
        try:
            ReadCSV.file = open("./data.csv" , "r")
            print("File opened")
            
            table = csv.reader(ReadCSV.file)
            print("Records are :")
            for record in table:
                print(record)

        except Exception as e:
            print("Exception :", e)

        finally:
            if ReadCSV.file != None:
                ReadCSV.file.close()
                print("File closed")
                
        return

ReadCSV.main()

Using nested for loop, we can split the record into fields also:

table = csv.reader(ReadCSV.file)
print("Records information :")
     for record in table:
         for field in record:
             print(field)

Construct Dictionary object from CSV file:

• Create one CSV file with account details.
• Read CSV file
• Create an Empty dictionary
• Define a class with identity Account.
• Construct Account object and update the object into dictionary.
• Finally, when we specify the account number(key), we have to display value(account details).

accounts.csv file:

Account.py:

import csv
class Account:
    def __init__(self, accno, name, balance):
        self.accno = accno
        self.name = name
        self.balance = balance
        return

Bank.py:

class Bank:
    accs_dict = dict()
    def details():
        while True:
            num = int(input("Enter account number : "))
            try:
                record = Bank.accs_dict.get(num)
                print("Details are :")
                print("Name : ", record.name)
                print("Balance :", record.balance)
            except Exception as e :
                print("Exception :", e)

            ch = input("Do you want to check another record(y/n) : ")
            if ch=='n':
                break
        return

CSVToDict.py:

class CSVtoDict:
    file = None
    def main():
        try:
            CSVtoDict.file = open("./accounts.csv" , "r")
            print("File opened")
            
            table = csv.reader(CSVtoDict.file)
            for record in table:
                num = int(record[0])
                name = record[1]
                balance = int(record[2])
            
                obj = Account(num, name, balance)
                Bank.accs_dict.update({num : obj})
                print(record , " updated to dictionary")

            Bank.details()
                
        except Exception as e:
            print("Exception :", e)

        finally:
            if CSVtoDict.file != None:
                CSVtoDict.file.close()
                print("File closed")
                
        return

CSVtoDict.main()

Output:

File opened
['1001', 'amar', '5000']  updated to dictionary
['1002', 'annie', '8000']  updated to dictionary
['1003', 'hareen', '7500']  updated to dictionary
['1004', 'satya', '9000']  updated to dictionary
Enter account number : 1002
Details are :
Name :  annie
Balance : 8000
Do you want to check another record(y/n) : y
Enter account number : 1004
Details are :
Name :  satya
Balance : 9000
Do you want to check another record(y/n) : n
File closed

Write code for following: