Python Files

reading the file means accessing the file's data
writing to the file means adding or changing data in the file
os.path.join() builds the file path for you so it will work on multiple operating systems
- ```
import os
os.path.join('Users', 'bob', 'st.txt')
```
  gives 'Users\\bob\\st.txt' on Windows machine and 'Users/bob/st.txt' on a Mac

Opening and Closing

can open a file in three modes
- 'r' reading only
- 'w' writing only
- 'w+' reading and writing
open([file_path], [mode])
- example:
```
 st = open('st.txt', 'w')
 st.write('hi from Python!')
 st.close()
```
- it creates the file if it doesn't exist
- must close files that you open file_name.close()

Option 1: 'with statement'

with open([file_path], [mode]) as [variable_name]:
     [your_code]

it automatically closes the file when it finishes

access file by variable_name.what_you_want_to_do

example:

with open('st.txt'. 'r') as file:
  print(file.read())

example:

with open('my_data.txt') as file:
  for line in file:               # reads in one line at a time
      line = line.strip()         # strips newlines
      print(line)                 # or do whatever else you want with it

Option 2: skip 'with' and open directly --- newer more shorthand way of doing it
```
for line in open([file_path]k, [mode]):
    [your code]
```
- doesn't automatically close file
can only read a file once when you open it so make sure to save it's contents in a variable or container if need to use them later
files are automatically closed when program is done

CSV Files

stands for comma separated values
every line represents a row in a spreadsheet
piece of data separated by a delimiter represents a cell

writing example:

import csv

with open('st.csv', 'w') as f:
  write = csv.writer(f, delimiter = ',')
  write.writerow(['one', 'two', 'three'])
  write.writerow(['four', 'five', 'six'])

will create the file st.csv

in a text editor it will look like:
```
one, two, three
four, five, six
```

in a spreadsheet:

____________________
|one  |two  |three |
____________________
|four |five | six  |
____________________

reading example:

import csv

with open('st.csv', 'r') as f:
  r = csv.reader(f, delimiter = ',')
  for row in r:
      print(','.join(row))

adds commas between each piece of data so it appears as it does in the original file

one, two, three
four, five, six