Syntax etc.¶
Syntax: Indentation (1)¶
Blocks and Indentation
Statements that end with a ‘
:’ introduce a blockBlocks are indented
End of a block is end of indentation
No explicit block delimiters (like ‘
{‘, ‘BEGIN’, …)Indentation is not only Coding Style, but also Syntax*
Careful, you experienced programmers!
New bug type: Indentation Bug
Syntax: Indentation (2)¶
i = 0
while i < 42:
print('Still not an answer: '+str(i))
i = i+1
print('The answer is: '+str(i))
Keep in mind …
Indentation must be consistent within one block
… can be mixed otherwise
Tune your editor’s knobs accordingly!
Syntax: Statements and Lines¶
Newline ends a statement …
answer = 42
Except … Multiline statements
answer = str(42) + \
', but only most of the time'
Braces |
Brackets |
Fun |
print(
"Hello",
"World")
|
message = [
"Hello",
"World"]
|
message = (
"Hello " +
"World")
|
Commandline Arguments¶
Python is lean:
Very few built-in functionality (compared to other languages)
Extension through modules
First (and most used):
sys
args.py¶#!/usr/bin/python
import sys
print(sys.argv[0])
print(sys.argv[1])
print(sys.argv[2])
$ ./x.py one argument
./x.py
one
argument
Comments vs. Documentation¶
As in many other script languages …
# this is a very important comment, which is
# definitely worth a read
Docstrings (slightly off-topic)
First string in a function, module, class, or method
Tools to generate documentation from it
def do_something(some_number):
""" Doing something with a number """
# some code here ...
>>> print(do_something.__doc__)
Doing something with a number