data.csv
        
Programming language
Designed by
Appeared
Extension
Python
Guido van Rossum
1991
.py
Java
James Gosling
1995
.java
C++
Bjarne Stroustrup
1983
.cpp
# A CSV file (Comma Separated Values file) is a type of plain text 
# file that uses specific structuring to arrange tabular data. Because
# it’s a plain text file, it can contain only actual text data—in 
# other words, printable ASCII or Unicode characters.

#import necessary modules

import csv
with open('./data.csv','rt')as f:
  data = csv.reader(f)
  for row in data:
        print(row)
        
# Normally, CSV files use a comma to separate each specific data value.
# Here’s what that structure looks like:

# column 1 name,column 2 name, column 3 name
# first row data 1,first row data 2,first row data 3
#second row data 1,second row data 2,second row data 3
# ...

# Normally, the first line identifies each piece of data—in other 
# words, the name of a data column. Every subsequent line after that 
# is actual data and is limited only by file size constraints.

['\ufeffProgramming language', 'Designed by', 'Appeared', 'Extension']
['Python', 'Guido van Rossum', '1991', '.py']
['Java', 'James Gosling', '1995', '.java']
['C++', 'Bjarne Stroustrup', '1983', '.cpp']

# the separator character is called a delimiter, and the comma is not
# the only one used. Other popular delimiters include the tab (\t), 
# colon (:) and semi-colon (;) characters. Properly parsing a CSV file
# requires us to know which delimiter is being used.

with open('./data.csv', newline='') as csvfile:
    data = csv.reader(csvfile, delimiter=',', quotechar='|')
    for row in data:
        print(','.join(row))

Programming language,Designed by,Appeared,Extension
Python,Guido van Rossum,1991,.py
Java,James Gosling,1995,.java
C++,Bjarne Stroustrup,1983,.cpp

employee_addresses.txt
name,address,date joined

john smith,1132 Anywhere Lane Hoboken NJ*, 07030,Jan 4

erica meyers,1234 Smith Lane Hoboken NJ*, 07030,March 2

# The reader object can handle different styles of CSV files by 
# specifying additional parameters, some of which are shown below:

# delimiter specifies the character used to separate each field. 
# The default is the comma (',').

# quotechar specifies the character used to surround fields that 
# contain the delimiter character. The default is a double quote 
# (' " ').

# escapechar specifies the character used to escape the delimiter 
# character, in case quotes aren’t used. The default is no escape 
# character.

with open('./employee_addresses.txt', newline='') as csvfile:
    data = csv.reader(csvfile, delimiter=',', quotechar='|', escapechar='/')
    for row in data:
        print(','.join(row))

name,address,date joined
john smith,1132 Anywhere Lane Hoboken NJ*, 07030,Jan 4
erica meyers,1234 Smith Lane Hoboken NJ*, 07030,March 2

bday.csv
   
John Smith
Accounting
November
Erica Meyers
IT
March
import csv
import petl as etl
bday = [['name','department','birthday month'],
['John Smith','Accounting','November'],
['Erica Meyers','IT','March']]

with open('bday.csv', 'w') as f:
    writer = csv.writer(f)
    writer.writerows(bday)
    
bday2 = etl.fromcsv('bday.csv'); bday2

name	department	birthday month
John Smith	Accounting	November
Erica Meyers	IT	March

with open('bday.csv', mode='w') as employee_file:
    employee_writer = csv.writer(employee_file, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL)

    employee_writer.writerow(['John Smith', 'Accounting', 'November'])
    employee_writer.writerow(['Erica Meyers', 'IT', 'March'])

employee_file2.csv
emp_name
dept
birth_month
John Smith
Accounting
November
Erica Meyers
IT
March
# Writing CSV file from a dictionary with csv:

import csv

with open('employee_file2.csv', mode='w') as csv_file:
    fieldnames = ['emp_name', 'dept', 'birth_month']
    writer = csv.DictWriter(csv_file, fieldnames=fieldnames)

    writer.writeheader()
    writer.writerow({'emp_name': 'John Smith', 'dept': 'Accounting', 'birth_month': 'November'})
    writer.writerow({'emp_name': 'Erica Meyers', 'dept': 'IT', 'birth_month': 'March'})    

employee_addresses.csv
 
name
address
date joined
john smith
1132 Anywhere Lane Hoboken NJ, 07030
Jan 4
erica meyers
1234 Smith Lane Hoboken NJ, 07030
March 2
import csv

with open('employee_addresses.txt', newline='') as csvfile, open('employee_addresses.csv', mode='w') as employee_file:
    data = csv.reader(csvfile, delimiter=',', quotechar='|', escapechar='*')
    employee_writer = csv.writer(employee_file, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL)
    employee_writer.writerow(data)

import csv

with open('employee_addresses.txt', newline='') as infile, open('employee_addresses.csv', mode='w', newline='') as outfile:
    reader = csv.DictReader(infile, delimiter=',', quotechar='|', escapechar='*')
    writer = csv.DictWriter(outfile, reader.fieldnames, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL)
    # copy rows over to new format
    writer.writeheader()
    writer.writerows(reader)

# with a loop which is not necessary;

import os
import csv

with open('./employee_addresses.txt', newline='') as csvfile:
    data = csv.reader(csvfile, delimiter=',', quotechar='|', escapechar='*')
    table = []
    for row in data:
        table.append(row)
        
with open('employee_addresses2.txt', mode='w') as employee_file:
    employee_writer = csv.writer(employee_file, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL)
    employee_writer.writerows(table)
            
os.rename(r'employee_addresses2.txt', r'employee_addresses.csv')            

import os
os.rename(r'employee_addresses2.txt', r'employee_addresses.csv')            

---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-11-23ba5a5622be> in <module>
      1 import os
----> 2 os.rename(r'employee_addresses2.txt', r'employee_addresses.csv')

FileNotFoundError: [Errno 2] No such file or directory: 'employee_addresses2.txt' -> 'employee_addresses.csv'

employee_birthday.txt
 
name,department,birthday month

John Smith,Accounting,November

Erica Meyers,IT,March
# or else: 

with open('employee_birthday.txt', mode='r') as csv_file:
    csv_reader = csv.DictReader(csv_file)
    line_count = 0
    for row in csv_reader:
        if line_count == 0:
            print(f'Column names are {", ".join(row)}')
            line_count += 1
        print(f'\t{row["name"]} works in the {row["department"]} department, and was born in {row["birthday month"]}.')
        line_count += 1
    print(f'Processed {line_count} lines.')
    
# Where did the dictionary keys come from? The first line of the CSV 
# file is assumed to contain the keys to use to build the dictionary. 
# If you don’t have these in your CSV file, you should specify your 
# own keys by setting the fieldnames optional parameter to a list 
# containing them.    

import os
print (os.getcwd())  # Prints the current working directory

os.chdir('.')  # Provide the new path here
print (os.getcwd()) 

pwd

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