update(python-cli): basic python cli application

issue #104

language/python/pythonBasicNotes.md

@@ -3,6 +3,9 @@
 <!-- TOC -->
 
 - [Python Basic Notes](#python-basic-notes)
+  - [CLI Application](#cli-application)
+    - [Basic CLI](#basic-cli)
+    - [Progress Bar](#progress-bar)
   - [Matplotlib Usage](#matplotlib-usage)
     - [Plot Type](#plot-type)
     - [Basic Usage](#basic-usage)
@@ -18,6 +21,98 @@
 
 <!-- /TOC -->
 
+## CLI Application
+
+### Basic CLI
+
+```python
+import click
+
+from caesar_encryption import encrypt
+
+@click.command()
+@click.option(
+    '--input_file',
+    type=click.File('r'),
+    help='File in which there is the text you want to encrypt/decrypt.'
+         'If not provided, a prompt will allow you to type the input text.',
+)
+@click.option(
+    '--output_file',
+    type=click.File('w'),
+    help='File in which the encrypted / decrypted text will be written.'
+         'If not provided, the output text will just be printed.',
+)
+@click.option(
+    '--decrypt/--encrypt',
+    '-d/-e',
+    help='Whether you want to encrypt the input text or decrypt it.'
+)
+@click.option(
+    '--key',
+    '-k',
+    default=1,
+    help='The numeric key to use for the caesar encryption / decryption.'
+)
+def caesar(input_file, output_file, decrypt, key):
+    if input_file:
+        text = input_file.read()
+    else:
+        text = click.prompt('Enter a text', hide_input=not decrypt)
+    if decrypt:
+        key = -key
+    cyphertext = encrypt(text, key)
+    if output_file:
+        output_file.write(cyphertext)
+    else:
+        click.echo(cyphertext)
+
+if __name__ == '__main__':
+    caesar()
+```
+
+### Progress Bar
+
+```python
+import click
+import enchant
+
+from tqdm import tqdm
+
+from caesar_encryption import encrypt
+
+@click.command()
+@click.option(
+    '--input_file',
+    type=click.File('r'),
+    required=True,
+)
+@click.option(
+    '--output_file',
+    type=click.File('w'),
+    required=True,
+)
+def caesar_breaker(input_file, output_file):
+    cyphertext = input_file.read()
+    english_dictionnary = enchant.Dict("en_US")
+    best_number_of_english_words = 0
+    for key in tqdm(range(26)):
+        plaintext = encrypt(cyphertext, -key)
+        number_of_english_words = 0
+        for word in plaintext.split(' '):
+            if word and english_dictionnary.check(word):
+                number_of_english_words += 1
+        if number_of_english_words > best_number_of_english_words:
+            best_number_of_english_words = number_of_english_words
+            best_plaintext = plaintext
+            best_key = key
+    click.echo(f'The most likely encryption key is {best_key}. It gives the following plaintext:\n\n{best_plaintext[:1000]}...')
+    output_file.write(best_plaintext)
+
+if __name__ == '__main__':
+    caesar_breaker()
+```
+
 ## Matplotlib Usage
 
 ```bash