current working directory

use the following code to see what your current working directory is

import os
current_working_directory = os.path.realpath('.')
print(current_working_directory)

whenever you open files without specifying a full path, the operating system will assume you are using this directory

look at a folder in windows file explorer

on windows OS only

use the following code to open the windows file explorer in your current working directory.
this will be useful when you’re looking for files you are creating

# windows only
import subprocess
current_working_directory = os.path.realpath('.')
if os.name == 'nt':
    subprocess.Popen('explorer.exe ' + current_working_directory)

notice how it opened a new window for you

write file

use the following code to open the file ex07.txt for writing
```
 f = open('ex07.txt', 'w')
```

here’s some text to write into the file

 dead_parrot = """
 I wish to complain about this parrot what I purchased not half an hour ago from this very boutique.

 Oh yes, the, uh, the Norwegian Blue...What's,uh...What's wrong with it?

 I'll tell you what's wrong with it, my lad. 'E's dead, that's what's wrong with it!

 No, no, 'e's uh,...he's resting.
 """

don’t forget to close the file
can you find this file on your hard drive?

reading a file

use open() and a for loop to read the contents of the "ex07.txt" file, line by line

convenience functions - read_file

Lets write a convenience function called readfile that accepts one parameter called filename

def readfile(filename):

the function should:

opens the file to a variable called f
reads and returns all the content of the file (use f.read())
closes the file

Also lets write convenience function called printfile that accepts one parameter called filename like so:

def printfile(filename):
    print(readfile(filename))

Lets use printfile function on 'ex07.txt' to read its contents

transforming a file

we want to write an ALL CAPS version of ex07.txt where all the text is in uppercase

open the ‘ex07.txt’ input file for reading
open a new ‘ex07.allcaps.txt’ output file for writing
use a for loop on the read file to read the text line by line
1. convert each line to uppercase
2. write the line to the output file
don’t forget to close the files
make sure the new file is there

renaming and deleting files

use the following code to delete the file "ex07.txt"
```
import os
os.remove('ex07.txt')
```
use the os.rename() function (use help to figure out how to use it) to rename the file 'ex07.allcaps.txt' to "ex07.txt"

now we’ve “rewritten” the ex07.txt file to be in all caps
but what really happened is that we wrote a new file, and then replaced the old file with the new file in most cases of working on files, this is the right way to approach problems and how many scripts, editors or programs work > in the real world

writing a CSV file

The so-called CSV (Comma Separated Values) format is the most common import and export format for spreadsheets and databases. CSV format was used for many years prior to attempts to describe the format in a standardized way in RFC 4180.

here’s a some information about bank customers, their name, current money in the bank, and the salary check that they have received

transactions = [
#    name             , money in bank now  , salary
    ['eric idle'      , 10000              , 5000  ],
    ['terry gilliam'  ,  2500              , 12500 ],
    ['graham chapman' , -5000              , 20000 ]
    ]

can you use a loop to write this, along with a header, to a CSV file named "transactions.csv"?

expected output in transactions.csv:

name, money in bank now, salary
eric idle, 10000, 5000
terry gilliam, 2500, 12500
graham chapman, 

transforming a CSV file

Lets compute how much money each bank customer will have after their salary kicks in and write the results into a new file called "totals.csv" this file needs only 2 columns - we drop the salary column

expected output for totals.csv:

name, money in bank now 
eric idle, 15000
terry gilliam, 15000
graham chapman, 15000

Creating and deleting directories

import the module shutil and use the shutil.rmtree('mydir1') function to remove a directory called mydir1 if it exists

CAREFUL: rmtree will delete whole folders and subdirectories without prompt and without recovery. like a rm -rf
use the os.mkdir() function to create a directory called mydir1 in the current working directory
use the os.makedirs() function to create a sub-directory called `mydir1/mydir2/mydir3’
create a file called surprise.txt in mydir1/mydir2/mydir3 and put the line 'nobody expects the spanish inquisition' into that file
convince yourself that os.remove() can delete files and empty directories, but cannot delete folders with ‘stuff’ in them

writing a JSON file

Create some complex object made of lists, tuples, dictionaries, strings, put it in variable named data example:

data = [{
     "userId":"rirani",
     "jobTitleName":"Developer",
     "firstName":"Romin",
     "lastName":"Irani",
     "preferredFullName":"Romin Irani",
     "employeeCode":"E1",
     "region":"CA",
     "phoneNumber":"408-1234567",
     "emailAddress":"romin.k.irani@gmail.com"
 },
 {
     "userId":"nirani",
     "jobTitleName":"Developer",
     "firstName":"Neil",
     "lastName":"Irani",
     "preferredFullName":"Neil Irani",
     "employeeCode":"E2",
     "region":"CA",
     "phoneNumber":"408-1111111",
     "emailAddress":"neilrirani@gmail.com"
 }]

use the open() function to open a file called data.json.txt into variable named fout
import the json module and use the json.dump(data, f) function to write your object to the file
close the file
open the file with a text editor program and compare with your original
use open() function to open the file for reading with variable fin
use the data2 = json.load(fin) function to read the file into a variable named data2
use == to compare data and data2. do they have the same content?