python核心编程学习笔记

1:

   raw_input()

2: 

 '//' stands for floating divide,and should know the difference between '/' and '//'

3:

'**' means power, for example 2**3 = 8; 2**1 = 2;

4:

enumerate， 

for example

for index, ch in enumerate(str): 

    print index

5:

In the operations of file, '+' = 'rw', and 'a' means that add something to the end of file.

6:

class Test(object):

    class_variable = 'andy'

    pass

The point is to understand how use 'class variable'

7:

sys.platform, sys.version

8:

functional helper method:

range(start, end, step);

type(obj)

dir(obj)

9:

understand how use '\' and ';'

10:

comprehend the follow lines

ls = os.linesep

a = ['and', 'hell']

file.writelines(["%s%s" % (x, ls) for x in a])

11:

understand the means of a[::n]

12:

 try to find the same and difference among the follow lines

(a)

  a = b = 2.0

(b) a = 2.0 ; b = a;

(c) a = 2.0;  b = 2.0;

(d) a = 2.0; b = 1.8 + 0.2

id(a) == id(b) == a is b

notes, int and string have another explains

when I test, python can cache from -5 to 257, and it will change, please don't use this property

13:

repr(s); return string

if inistance (num, (int, long):

    print 'hellp'

14: 

max and reduce

http://blog./2008/02/19/python-function-max-and-reduce/

sort(reverse=True) stands for descending order

enumerate(a) generate [index, column]

15:

How to use zip

a = [1, 2]; b =['a', 'b']

zip(a,b); return [(1, 'a'), (2, 'b')]

test = zip(a,b)

c, d = zip(*test) 

http://apps.hi.baidu.com/share/detail/35028002

16:

Generally speeking, in consideration of performance, we should not write repeated funtion call in the circle. For example:

while i < len(my_string):

    print i

we shoud do like follow:

length = len(my_string)

while i < lenght:

    pass

In addition 

for substring in my_string[1:]

   if substring not in a + b

       pass

17

from string import Template

s = Template("I'm ${name}")

pritn s.substitute(name="andy")