little things

Akuli · Akuli · commit 85108ad1da96 · 2016-10-30T15:27:59.000+02:00
diff --git a/README.md b/README.md
@@ -11,23 +11,18 @@ you have programmed a lot in the past using some other language you
 probably want to read
 [the official tutorial](https://docs.python.org/3/tutorial/) instead.
 
-This tutorial uses Python 3, and you need Python 3 to be able to run the
-example code yourself. Python 2 is getting outdated all the time,
-and more and more projects are moving to Python 3. There are a few
-popular libraries that don't support Python 3 that well at the time of
-writing this, but you don't need to worry about that just yet. They
-will probably support Python 3 by the time you've learned the basics
-and you may actually need them.
+This tutorial was written in Python 3, and you need Python 3 or newer to
+be able to run the example code yourself. Python 2 is getting outdated
+all the time, and more and more projects are moving to Python 3. There
+are a few popular libraries that don't support Python 3 that well at the
+time of writing this, but you don't need to worry about that just yet.
+They will probably support Python 3 by the time you've learned the
+basics and you may actually need them.
 
 I have tested most of the code in this tutorial on Python 3.4, but
-everything should also work on any Python 3 version or newer.
+everything should also work on Python 3.2 and all newer Pythons.
 
-Here's a list of chapters in this tutorial. Read them one by one in the
-order they are listed. **If you jump to a chapter without reading and
-understanding everything before it, you may have hard time understanding
-the chapter you're trying to read.** However, the chapters are mostly
-independent from each other, so you can also use this tutorial together
-with other tutorials.
+## List of contents
 
 1. [What is programming?](what-is-programming.md)
 2. [Installing Python](installing-python.md)
diff --git a/exceptions.md b/exceptions.md
@@ -401,7 +401,7 @@ all of these errors. You don't need to remember this tree, running
 `help('builtins')` should display a larger tree that this is a part of.
 
 There's also a few exceptions that are not in this tree like SystemExit
-and KeyboardInterrupt, but most of the time you shouldn't catch them.
+and KeyboardInterrupt, but most of the time we shouldn't catch them.
 Catching Exception doesn't catch them either.
 
 ## Summary
diff --git a/getting-started.md b/getting-started.md
@@ -206,7 +206,7 @@ Powers are calculated before `*` and `/`, but after `()`.
 ## Summary
 
 - Errors don't matter.
-- You can enter any Python commands to the interactive `>>>` prompt, and
+- We can enter any Python commands to the interactive `>>>` prompt, and
     it will echo back the result.
 - Pieces of text starting with a `#` are comments.
 - `+`, `-`, `*` and `/` work in Python just like in math.
diff --git a/handy-stuff-strings.md b/handy-stuff-strings.md
@@ -321,7 +321,7 @@ If you need to know more about formatting I recommend reading
 
     ![Slicing](images/slicing3.png)
 
-- Indexing returns one character of a string. Remember that you don't
+- Indexing returns one character of a string. Remember that we don't
     need a `:` with indexing. The indexes work like this:
 
     ![Indexing](images/indexing3.png)
diff --git a/if.md b/if.md
@@ -280,7 +280,7 @@ else:
     If it doesn't, write it to a file and run that file.
 - Indentation is important in Python.
 - Indented code under an if statement runs if the condition is true.
-- You can also add an else statement. Indented code under it will run
+- We can also add an else statement. Indented code under it will run
     if the code under the if statement does not run.
 - elif is short for else if.
 
diff --git a/images/modules.png b/images/modules.png
diff --git a/modules.md b/modules.md
@@ -46,7 +46,7 @@ OSX.
 You'll see a bunch of files and a few directories in the folder
 that opens:
 
-**TODO: Add a screenshot.**
+![My Python's modules.](images/modules.png)
 
 All of these `.py` files can be imported like we just imported
 `random.py`. In random.py, there's a like like `randint = something`,
@@ -175,7 +175,7 @@ module in many files, so it gets imported multiple times. If
 Python would reload the module every time it's imported,
 dividing code to multiple files would make the code run slower.
 
-If you want to load the module again, just exit out of Python and
+If we need to load the module again we can just exit out of Python and
 launch it again.
 
 ## Brief overview of the standard library
@@ -473,16 +473,16 @@ section at the bottom.
 
 ## Summary
 
-- Most modules are files on your computer, but some of them are built
+- Most modules are files on our computers, but some of them are built
     in to Python. We can use modules in our projects by importing them,
     and after that using `modulename.variable` to get a variable from
     the module.
 - Some of the most commonly used modules are random, sys, math, time
     and os.
 - Avoid creating `.py` files that have the same name as a name of a
     module you want to use.
-- Python comes with many modules, and you can install even more modules
-    if you want to.
+- Python comes with many modules, and we can install even more modules
+    if we want to.
 
 ***
 
diff --git a/using-functions.md b/using-functions.md
@@ -77,7 +77,7 @@ Of course, `x = print('hello')` is useless compared to `print('hello')`
 because the print function always returns None and we can do `x = None`
 without any printing.
 
-You can also print an empty line by calling print without any
+We can also print an empty line by calling print without any
 arguments:
 
 ```py
@@ -96,7 +96,7 @@ world
 >>> 
 ```
 
-If you want to print a backslash, you need to **escape** it by typing
+If we want to print a backslash, we need to **escape** it by typing
 two backslashes:
 
 [comment]: # (For some reason, GitHub's syntax highlighting doesn't)
@@ -106,8 +106,8 @@ two backslashes:
     hello\nworld
     >>> 
 
-You can also pass multiple arguments to the print function. Separate
-them with commas, and print will add spaces between them.
+We can also pass multiple arguments to the print function. We need to
+separate them with commas and print will add spaces between them.
 
 ```py
 >>> print("Hello", "World!")
@@ -139,7 +139,7 @@ screen and waited for me to type something. I typed hello and pressed
 Enter. Then input returned the hello I typed as a string and it was
 assigned to x.
 
-You may want to add a space after the `:`, like this:
+Usually we want to add a space after the `:`, like this:
 
 ```py
 >>> x = input("Enter something: ")  # now there's space between : and where i type
diff --git a/variables.md b/variables.md
@@ -71,7 +71,7 @@ without variables.
 
 Variable names can be multiple characters long. They can contain
 uppercase characters, numbers and some other characters, but most of the
-time you should use simple, lowercase variable names. You can also use
+time we should use simple, lowercase variable names. You can also use
 underscores.
 
 ```py
@@ -97,7 +97,7 @@ Variable names are case-sensitive, like many other things in Python.
 
 Python also has some words that cannot be used as variable names
 because they have a special meaning. They are called **keywords**, and
-you can run `help('keywords')` to see the full list if you want to.
+we can run `help('keywords')` to see the full list if we want to.
 We'll learn to use most of them later in this tutorial. Trying to use a
 keyword as a variable name causes a syntax error.
 
@@ -146,7 +146,7 @@ This is not limited to integers.
 >>> 
 ```
 
-Now you also understand why typing hello to the prompt didn't work in
+Now we also understand why typing hello to the prompt didn't work in
 the beginning of this tutorial. But we can assign something to a
 variable called hello and then type hello:
 
@@ -174,7 +174,7 @@ False
 ```
 
 `a == 1` is the same as `(a == 1) == True`, but `a == 1` is more
-readable, so most of the time you shouldn't write `== True` anywhere.
+readable, so most of the time we shouldn't write `== True` anywhere.
 
 ```py
 >>> a = 1
@@ -213,14 +213,30 @@ This is because the prompt never echoes back None. That is handy,
 because many things result in None, and it would be annoying to see
 None coming up all the time.
 
-If we want to see a None on the interactive prompt, we can use print:
+If we want to see a None on the interactive prompt, we can use print.
 
 ```py
 >>> print(thingy)
 None
 >>> 
 ```
 
+Another confusing thing is that if we do something weird to None we get
+error messages that talk about NoneType object. The NoneType object they
+are talking about is always None.
+
+```py
+>>> None.hello    # None has no attribute 'hello'
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+AttributeError: 'NoneType' object has no attribute 'hello'
+>>> None()        # None is not callable
+Traceback (most recent call last):
+  File "<stdin>", line 1, in <module>
+TypeError: 'NoneType' object is not callable
+>>> 
+```
+
 ## Other comparing operators
 
 So far we've used `==`, but there are other operators also. At this
@@ -230,21 +246,20 @@ easy to learn.
 | Usage     | Description                       | True examples         |
 |-----------|-----------------------------------|-----------------------|
 | `a == b`  | a is equal to b                   | `1 == 1`              |
-| `a != b`  | a is not equal to b               | `1 == 2`              |
+| `a != b`  | a is not equal to b               | `1 != 2`              |
 | `a > b`   | a is greater than b               | `2 > 1`               |
 | `a >= b`  | a is greater than or equal to b   | `2 >= 1`, `1 >= 1`    |
 | `a < b`   | a is less than b                  | `1 < 2`               |
 | `a <= b`  | a is less than or equal to b      | `1 <= 2`, `1 <= 1`    |
 
-We can also combine multiple comparisons.
+We can also combine multiple comparisons. This table assumes that a and
+b are Booleans.
 
 | Usage     | Description                               | True example                      |
 |-----------|-------------------------------------------|-----------------------------------|
 | `a and b` | a is True and b is True                   | `1 == 1 and 2 == 2`               |
 | `a or b`  | a is True, b is True or they're both True | `False or 1 == 1`, `True or True` |
 
-This table assumes that a and b are Booleans.
-
 Another way to combine operations is chaining. For example, `a < b < c`
 does the same thing as `a < b and b < c`.
 
