Finish string course 2

docs/blog/posts/20240627_python_course_2.md

@@ -81,3 +81,57 @@ Get ready to join the thriving Python community, let's get started!
     |---------|-----|-----|----|----|----|----|----|----|----|----|----|
     | + index | 0   | 1   | 2  | 3  | 4  | 5  | 6  | 7  | 8  | 9  | 10 |
     | - index | -11 | -10 | -9 | -8 | -7 | -6 | -5 | -4 | -3 | -2 | -1 |
+
+## Formatted Strings
+
+- We don't need string concatenation all the time:
+
+    ```python
+    first_name = 'Gabriel'
+    last_name = 'Dornas'
+    full_name = f'{first_name} {last_name}' # (1)!
+    message = f'Hello {full_name}, is everything ok with you?' # (2)!
+    print(message)
+    ```
+
+    1. :man_raising_hand: The same as using string concatenation or the expression `first_name + last_name`.
+    2. :man_raising_hand: Mix text and variables to create new `str`.
+
+## String methods
+
+- Tons of code already available to use[^1]:
+
+    ```python
+    course = 'All we need is Python!'
+
+    # lenght
+    print(len(course)) # (1)!
+
+    # uppercase
+    print(course.upper()) # (2)!
+
+    # lowercase
+    print(course.lower()) # (3)!
+
+    # find
+    print(course.find('P')) # (4)!
+
+    # replace
+    print(course.replace('Python', 'love')) # (5)!
+
+    # in operator
+    print('Python' in course) # (6)!
+    ```
+
+    1. :man_raising_hand: Could be used, for example, to restrict the number of characters in a form's input filed.
+    2. :man_raising_hand: The `.upper()` method doesn't change the original `str`. Try to `print(course)` to check it.
+    3. :man_raising_hand: As in the `.upper()` method, the `.lower()` doesn't change the original `str`. Try to `print(course)` to check it.
+    4. :man_raising_hand: The `.find()` returns the index of the first occurrence of the searched character, in this example `P`. It is case sensitive, try to pass `p` to `.find()` to see the result.
+    5. :man_raising_hand: It's case sensitive just like we saw in the `.find()` method. Try to pass `python` to `.replace()` to see the result.
+    6. :man_raising_hand: This is called a boolean expression. This is case sensitive just like we saw in the `.find()` and in the `replace()` methods. Try to pass `python` to it to see the result.
+
+??? question "Could you tell the difference between the `find()` method and the `in` operator?"
+
+    While both `find()` and `in` help search in Python, they serve different purposes. Use `in` for a quick existence check,**returning a boolean value (True/False)**. If you specifically need the position of a substring within a string, then `find()` is the way to go, **returning the index of the first occurrence**.
+
+[^1]: Check [other `str` built-in methods](https://www.w3schools.com/python/python_ref_string.asp) that you can use in Python.