Chapter 06 | Storing and Manipulating Data | Where to put your data

In the web application we built in the last chapter, we will try to find the answer's to these question in the present chapter

Open | Process | Close

The most easy way to store data is in text file.
Python comes with built-in support for open, process, close
- open : Open a file
- process : process its data in some way
- close : close the file when finished.
todos = open('todo.txt', 'a')
- It open a file name todo.txt.
- The file is opened in a, i.e. append mode.
- todos is the file stream.
print("text", file=todos) + print() takes an argument file, which redirect the text to the file.
todos.close() : The open files stream should be closed, else we can loose the data.

To read a file we can open() the file in default mode, which is the read mode.

tasks = open('todo.txt')

for chore in tasks:
    print(chore)

tasks.close()

In the above code todo.txt is opened in read mode.
The python for loop when used with a file stream is intelligent enough to read a line of data from the file each time the loop operates.
There is already new line at the end of each line in the file, in addition print() adds extra line, we can pass end="" to stop that extra line.
Modes of file open :
- 'r' : Open a file for reading.
- 'w' : Open the file for writing. It empty the file content if present.
- 'a' : Open the file for append. The old content of the file is preserved.
- 'x' : Open a new file, throws error if file exist.
'b' : The above modes of file open is for textual data, if the file has binary data, append the above modes with 'b', like 'ab' or a+b.

with statement is preferred in place of the open, process and close stages.

with open('todos.txt') as task:
    for chore in tasks:
        print(chore, end="")

with statement is smart enough to remember to call close on our behalf.
with statement conforms to a coding convention called context management protocol.
with statement manages the context within the block it runs.
.read() : reads the complete content of the file and loads into memory.
escape() : Flask provides a function called escape which escape's based on HTML template.

'|'.join("hello", "brother") : joins the two words using the | as the separator.
.split('separator') : splits a string to list based on the separator supplied.