drop support for old pythons

README.md

@@ -12,7 +12,7 @@ or very little programming experience. If you have programmed a lot in
 the past using some other language you may want to read [the official
 tutorial](https://docs.python.org/3/tutorial/) instead.
 
-You can use Python 3.3 or any newer Python with this tutorial. **Don't
+You can use Python 3.5 or any newer Python with this tutorial. **Don't
 use Python 2 because it's no longer supported.**
 
 ## List of contents

advanced/datatypes.md

@@ -316,68 +316,25 @@ TypeError: unsupported operand type(s) for +: 'dict' and 'dict'
 >>>
 ```
 
-Dictionaries have an `update` method that adds everything from another
-dictionary into it. So we can merge dictionaries like this:
+Usually it's easiest to do this:
 
 ```python
->>> merged = {}
->>> merged.update({'a': 1, 'b': 2})
->>> merged.update({'c': 3})
->>> merged
-{'c': 3, 'b': 2, 'a': 1}
->>>
-```
-
-Or we can [write a function](../basics/defining-functions.md) like this:
-
-```python
->>> def merge_dicts(dictlist):
-...     result = {}
-...     for dictionary in dictlist:
-...         result.update(dictionary)
-...     return result
-...
->>> merge_dicts([{'a': 1, 'b': 2}, {'c': 3}])
-{'c': 3, 'b': 2, 'a': 1}
->>>
+>>> dict1 = {'a': 1, 'b': 2}
+>>> dict2 = {'c': 3}
+>>> {**dict1, **dict2}
+{'a': 1, 'b': 2, 'c': 3}
 ```
 
-Kind of like counting things, merging dictionaries is also a commonly
-needed thing and there's a class just for it in the `collections`
-module. It's called ChainMap:
+Dictionaries also have an `update` method that adds everything from another
+dictionary into it, and you can use that too. This was the most common way to
+do it before Python supported `{**dict1, **dict2}`.
 
 ```python
->>> import collections
->>> merged = collections.ChainMap({'a': 1, 'b': 2}, {'c': 3})
+>>> merged = {}
+>>> merged.update({'a': 1, 'b': 2})
+>>> merged.update({'c': 3})
 >>> merged
-ChainMap({'b': 2, 'a': 1}, {'c': 3})
->>>
-```
-
-Our `merged` is kind of like the Counter object we created earlier. It's
-not a dictionary, but it behaves like a dictionary.
-
-```python
->>> for key, value in merged.items():
-...     print(key, value)
-...
-c 3
-b 2
-a 1
->>> dict(merged)
-{'c': 3, 'b': 2, 'a': 1}
->>>
-```
-
-Starting with Python 3.5 it's possible to merge dictionaries like this.
-**Don't do this unless you are sure that no-one will need to run your
-code on Python versions older than 3.5.**
-
-```python
->>> first = {'a': 1, 'b': 2}
->>> second = {'c': 3, 'd': 4}
->>> {**first, **second}
-{'d': 4, 'c': 3, 'a': 1, 'b': 2}
+{'a': 1, 'b': 2, 'c': 3}
 >>>
 ```
 

basics/exceptions.md

@@ -319,7 +319,7 @@ it's usually better to use `sys.stderr` and `sys.exit`.
 ## Exception hierarchy
 
 Exceptions are organized like this. I made this tree with [this
-program](https://github.com/Akuli/classtree/) on Python 3.4. You may
+program](https://github.com/Akuli/classtree/) on Python 3.7. You may
 have more or less exceptions than I have if your Python is newer or
 older than mine, but they should be mostly similar.
 
@@ -333,6 +333,7 @@ older than mine, but they should be mostly similar.
     ├── BufferError
     ├── EOFError
     ├── ImportError
+    │   └── ModuleNotFoundError
     ├── LookupError
     │   ├── IndexError
     │   └── KeyError
@@ -357,7 +358,9 @@ older than mine, but they should be mostly similar.
     │   └── TimeoutError
     ├── ReferenceError
     ├── RuntimeError
-    │   └── NotImplementedError
+    │   ├── NotImplementedError
+    │   └── RecursionError
+    ├── StopAsyncIteration
     ├── StopIteration
     ├── SyntaxError
     │   └── IndentationError

basics/modules.md

@@ -28,17 +28,17 @@ gave us?
 
 ```python
 >>> random
-<module 'random' from '/usr/lib/python3.4/random.py'>
+<module 'random' from '/usr/lib/python3.7/random.py'>
 >>>
 ```
 
 So it's a module, and it comes from a path... but what does
 all that mean?
 
-Now open the folder that contains your `random.py` is. On my
-system it's `/usr/lib/python3.4`, but yours will probably be
+Now open the folder that contains your `random.py`. On my
+system it's `/usr/lib/python3.7`, but yours will probably be
 different. To open a folder in your file manager you can press
-Windows-R on Windows or Alt+F2 on most GNU/Linux distributions,
+Windows-R on Windows or Alt+F2 on most Linux distributions,
 and just type your path there. I don't have an up-to-date copy
 of OSX so unfortunately I have no idea what you need to do on
 OSX.
@@ -138,11 +138,11 @@ places that modules are searched from:
 <module 'sys' (built-in)>
 >>> sys.path
 ['',
- '/usr/lib/python3.4',
- '/usr/lib/python3.4/plat-i386-linux-gnu',
- '/usr/lib/python3.4/lib-dynload',
- '/home/akuli/.local/lib/python3.4/site-packages',
- '/usr/local/lib/python3.4/dist-packages',
+ '/usr/lib/python37.zip',
+ '/usr/lib/python3.7',
+ '/usr/lib/python3.7/lib-dynload',
+ '/home/akuli/.local/lib/python3.7/site-packages',
+ '/usr/local/lib/python3.7/dist-packages',
  '/usr/lib/python3/dist-packages']
 >>>
 ```
@@ -234,9 +234,9 @@ hello
 >>>
 >>> # information about Python's version, behaves like a tuple
 >>> sys.version_info
-sys.version_info(major=3, minor=4, micro=2, releaselevel='final', serial=0)
->>> sys.version_info[:3]  # this is Python 3.4.2
-(3, 4, 2)
+sys.version_info(major=3, minor=7, micro=3, releaselevel='final', serial=0)
+>>> sys.version_info[:3]  # this is Python 3.7.3
+(3, 7, 3)
 >>>
 >>> sys.exit()  # exit out of Python
 ```