https://docs.python.org/2.7/faq/programming.html
2. Python module search path
https://docs.python.org/2.7/tutorial/modules.html#the-module-search-path
If you do an "import syslib", how does the python locate the library?
1. local directory <<<< surprised?!
2. PYTHONPATH
so if you have a locally mistaken syslib.py or syslib.pyc under the local directory, you gonna break this import. And if you see something wanky, print cmd.__file__ will be helpful (or cmd.__version__)
3. Python Set
https://docs.python.org/3/tutorial/datastructures.html#sets
- {} and set() can be used to create set
- But to create an empty one, must use set(), not {} which is to create a dictionary.
- set_ = {0}
4. 3 Ways to delete an element in a list
1) most efficient - del List[idx]
2) less efficient if need to have the element - List.pop(idx)
3) lest effificient - slice, List[:i] + List[i+1:]
5. Python reduce, filter
>>> l = [1,2,3,4]
>>> reduce( (lambda x,y: x*10+y), l)
1234
>>> reduce( (lambda x,y: x*100+y), l)
1020304
>>> l = range(1, 100, 5)
>>> l
[1, 6, 11, 16, 21, 26, 31, 36, 41, 46, 51, 56, 61, 66, 71, 76, 81, 86, 91, 96]
>>> filter(lambda x:x%4, l)
[1, 6, 11, 21, 26, 31, 41, 46, 51, 61, 66, 71, 81, 86, 91]
6. Python Naming Convention
http://legacy.python.org/dev/peps/pep-0008/#code-lay-out
2) less efficient if need to have the element - List.pop(idx)
3) lest effificient - slice, List[:i] + List[i+1:]
5. Python reduce, filter
>>> l = [1,2,3,4]
>>> reduce( (lambda x,y: x*10+y), l)
1234
>>> reduce( (lambda x,y: x*100+y), l)
1020304
>>> l = range(1, 100, 5)
>>> l
[1, 6, 11, 16, 21, 26, 31, 36, 41, 46, 51, 56, 61, 66, 71, 76, 81, 86, 91, 96]
>>> filter(lambda x:x%4, l)
[1, 6, 11, 21, 26, 31, 41, 46, 51, 61, 66, 71, 81, 86, 91]
6. Python Naming Convention
http://legacy.python.org/dev/peps/pep-0008/#code-lay-out
- limit all lines to 79，docstring/comment to 72
class Rectangle(Blob):
def __init__(self, width, height,
color='black', emphasis=None, highlight=0):
if (width == 0 and height == 0 and
color == 'red' and emphasis == 'strong' or
highlight > 100):
raise ValueError("sorry, you lose")
if width == 0 and height == 0 and (color == 'red' or
emphasis is None):
raise ValueError("I don't think so -- values are %s, %s" %
(width, height))
Blob.__init__(self, width, height,
color, emphasis, highlight)
- Module: short,
- all-lower-case name, like pystock.py
- Class: CapWords, like
- StockHist, StockInfo, StockERHist
- Function:
- lower_case_with_underscore
- Method and instance:
- lower_case_with_underscore
- Constants:
- ALL_CAPITALS_WITH_UNDERSCORE
- Internal attribute:
- _single_leading_underscore
- NOT imported.
- empty sequence = FALSE, so
- YES: if not seq:...
- NO: if len(seq)
- Attributes:
- self.lower_case_with_underscore
