Merge pull request #64 from aravinds-arv/aravind

Fixing some errors in Lessons 0, 1 & 2

.gitignore

@@ -0,0 +1,160 @@
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# poetry
+#   Similar to Pipfile.lock, it is generally recommended to include poetry.lock in version control.
+#   This is especially recommended for binary packages to ensure reproducibility, and is more
+#   commonly ignored for libraries.
+#   https://python-poetry.org/docs/basic-usage/#commit-your-poetrylock-file-to-version-control
+#poetry.lock
+
+# pdm
+#   Similar to Pipfile.lock, it is generally recommended to include pdm.lock in version control.
+#pdm.lock
+#   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
+#   in version control.
+#   https://pdm.fming.dev/#use-with-ide
+.pdm.toml
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# PyCharm
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/

docs/chapter-0/lesson-0.md

@@ -3,7 +3,7 @@
 ## What is Python?
 To answer this question, we need to first ask _What is a programming language?_ A **programming language** is essentially a language in which you can tell your computer what to do. You will understand what that means as start programming. Every programming language has its own strengths and purposes. **Python** is a general-purpose programming language that can be used for a wide variety of purposes including but not limited to data science, automation, machine learning and  software and web development. A typical python program to find the sum of the first 100 numbers looks like this:
 
-```python
+```python linenums="1"
 sum = 0
 for number in range(1, 101):
   sum += number
@@ -96,7 +96,7 @@ We will be using Python-3.8 or higher throughout these lessons. If some of you a
 
 ## Setting up Replit
 
-Replit is an online environment where we can write code. It is an ideal place to learn programming and we will be using it extensively in this course. Head to http://www.replit.com/ and sign up using your Online Degree account. Replit provides an excellent [tutorial](https://docs.replit.com/tutorials/01-introduction-to-the-repl-it-ide) to get you started.
+Replit is an online environment where we can write code. It is an ideal place to learn programming and we will be using it extensively in this course. Head to [replit.com](http://www.replit.com/) and sign up using your Online Degree account. Replit provides an excellent [tutorial](https://docs.replit.com/getting-started/intro-replit) to get you started.
 
 ## Installing Python on your System
 
@@ -125,4 +125,4 @@ Python is 30 years old. Programmers who boarded the Python-bus 30 years back lov
 2. Have a look at this interesting [interview](https://blog.dropbox.com/topics/work-culture/-the-mind-at-work--guido-van-rossum-on-how-python-makes-thinking) of Guido Van Rossum. This is a blog maintained by Dropbox. Another trivia: Guido worked at Dropbox for six and a half years. 
 3. Try to watch documentaries and interviews on the web where Guido talks about how Python came into existence. It is always good to know about some non-technical aspects of the language, such as its history and something about the people who were behind its development. It gives a humanistic flavor to technology. We often forget that a lot of software is written by humans, for humans.
 4. In the next few weeks to come, [StackOverflow](https://stackoverflow.com/) might become the most visited website by most of you. Some of you might be familiar with it, but for the others, StackOverflow is a question-answer forum for programming related questions. It is extremely popular not just among beginners but even experienced developers. Do check it out, but use it wisely. Refrain from using it to get answers to assignment questions; you won't learn anything that way.
-5. You can also look into the official documentation on the python [website]((https://docs.python.org/3/)).
+5. You can also look into the official documentation on the python [website](https://docs.python.org/3/).

docs/chapter-1/lesson-1.1.md

@@ -40,7 +40,7 @@ Hello World!
 
 The sentence enclosed by the parentheses of the `#!py print()` function is called a **string**. A **string** is a sequence of characters enclosed in quotes. Strings can either be in single quotes or double quotes. However, a single quote can't be matched against a double quote to enclose a string. We have used single quotes in line 1 and double quotes in line 3. Both lines give identical outputs. The ability to use both single quotes and double quotes comes in handy in situations like this:
 
-!!! question "Problem" 
+!!! question " " 
     Print a string that has an apostrophe in it:
 
 ```pycon

docs/chapter-1/lesson-1.2.md

@@ -178,14 +178,14 @@ True
 
 ### Operator Chaining
 
-    Python supports chaining relational operators. This enables you to evaluate chains of comparison without having to use logical operators. 
-    ```python
-    >>> 10 < 11 <= 12
-    True
-    # is the same as
-    >>> 10 < 11 and 11 <= 12
-    True
-    ```
+Python supports chaining relational operators. This enables you to evaluate chains of comparison without having to use logical operators. 
+```python
+>>> 10 < 11 <= 12
+True
+# is the same as
+>>> 10 < 11 and 11 <= 12
+True
+```
 
 ## Expressions
 
@@ -281,4 +281,4 @@ We can take the help of a concept called **truth table** to analyze the outcomes
 |  True   |  False  |  True    |
 |  False  |  True   |  True    |
 |  False  |  False  |  False   |
-</div>
+</div>

docs/chapter-1/lesson-1.4.md

@@ -92,7 +92,7 @@ The interpreter throws a `TypeError`. The message accompanying the error is more
 
 The next exception that we will frequently encounter is `NameError`. 
 
-```python
+```python linenums="1"
 print('There is no problem with this line')
 print(x ** 2)
 ```

docs/chapter-1/lesson-1.5.md

@@ -26,7 +26,7 @@ third line
 
 The following code will throw a `SyntaxError`:
 
-```python
+```python linenums="1"
 x = 'first line
 second line
 third line'
@@ -35,7 +35,7 @@ print(x)
 
 This is where `'''` comes in:
 
-```python
+```python linenums="1"
 x = '''first line
 second line
 third line'''
@@ -56,21 +56,21 @@ The `\n` character that you see above is called a newline character. Head to the
 
 The length of a string is the number of characters in it. Python provides a built-in function called `len` to find the length of a string:
 
-```python
+```python linenums="1"
 x = 'good'
 print(len(x))
 ```
 
 The code given above will give 4 as the output. If you are familiar with other programming languages, such as C, you might be aware of a character data type. Python doesn't have a separate data type for characters. A character in Python is represented by a string of length 1. In the following examples, `x` and `y` are strings of length 1.
 
-```python
+```python linenums="1"
 x = 'a'
 y = 'b'
 ```
 
 We can also define empty strings:
 
-```python
+```python linenums="1"
 x = ''
 print(len(x))
 ```
@@ -85,7 +85,7 @@ As expected, the length of the empty string is 0.
 
 We can concatenate two strings using the `+` operator. Concatenation is just a fancy term for joining two strings together:
 
-```python
+```python linenums="1"
 string1 = 'first'
 string2 = ','
 string3 = 'second'
@@ -105,7 +105,7 @@ first,second
 
 We can make multiple copies of a string and string them all together using the `*` operator:
 
-```python
+```python linenums="1"
 s = 'good'
 five_s = s * 5
 print(five_s)
@@ -119,7 +119,7 @@ goodgoodgoodgoodgood
 
 The `*` operator has made the string look too good! This is a fine demonstration of that ancient adage: "multiplication is repeated addition":
 
-```python
+```python linenums="1"
 s = 'good'
 s * 5 == s + s + s + s + s	# This expression evaluates to True
 ```
@@ -130,7 +130,7 @@ s * 5 == s + s + s + s + s	# This expression evaluates to True
 
 We can compare two strings. To begin with, we have the `==` operator:
 
-```python
+```python linenums="1"
 x = 'python'
 print(x == 'python', x == 'nohtyp')
 ```
@@ -143,7 +143,7 @@ True False
 
 Two strings are equal if and only if both of them represent exactly the same sequence of characters.  Now, consider the following lines of code:
 
-```python
+```python linenums="1"
 print('good' > 'bad')
 print('nine' < 'one' )
 print('a' < 'ab' < 'abc' < 'b')
@@ -169,14 +169,14 @@ Python’s string type uses the Unicode standard for representing characters, wh
 
 Python provides a built-in function called `ord` that returns the code point of any given character. For example:
 
-```python
+```python linenums="1"
 print(ord('a'), ord('b'))
 print(ord('a'), ord('A'))
 ```
 
 The output is:
 
-```python
+```
 97 98
 97 65
 ```
@@ -189,7 +189,7 @@ Now, we clearly see why `'a' < 'b'` returns `True`. This is because the code poi
 
 In Python, the backslash -  `\` - is called the escape character. One of its uses is to represent certain white-space characters such as tabs and newlines. We will look at them one by one using the following examples:
 
-```python
+```python linenums="1"
 print('This is the first sentence.\nThis is the second sentence.')
 ```
 
@@ -202,7 +202,7 @@ This is the second sentence.
 
 `\n` is a newline character. Its effect is to introduce a new line. Note that even though there are two separate characters: `\` and `n`, `\n` is still regarded as a single character. To verify this, execute the following code. You should get 1 as the output.
 
-```python
+```python linenums="1"
 x = '\n'
 print(len(x))
 ```
@@ -239,7 +239,7 @@ Now remove the backslash from the above string and try to print it. You will get
 
 A string is a substring of another string if the first string is contained in the second. For example, `'good'` is a substring of `'very good'`, whereas `'very good'` is not a substring of `'verygood'`. Python provides a keyword - `in` - which can be used to check if a given string is a substring of another string. For example:
 
-```python
+```python linenums="1"
 a = 'good'
 b = 'very good'
 present = a in b
@@ -257,7 +257,7 @@ False
 
 `in` is a powerful keyword which has several other uses. It can also be used along with `not` in the following manner:
 
-```python
+```python linenums="1"
 a = 'abc'
 b = 'ab'
 print(a not in b)