2012-10-15 09:55
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彩虹炫 |
匿名卡 | 编辑 删除 Tom
- 1. zip((1,2,3),(7,8) ==> [(1,7),(2,8)]; zip(list/tuple, list/tuple, ...); no (3,-)
2. enumerate([7,8,9]) ==> {(0,7),(1,8),(2,9)}; enumerate(list | tuple | set | range)
3. @myDecorator : to change the following decorated function for probing
3a. myDecorator can be a class or function
3b. if class, class myDecorator(object):
def __init__(self,f): self.f = f;
def __call__(self): ...self.f()...;
3c. if function, def myDecorator(f): def new_f():...f()...; return new_f;
3d. @A; def f():pass; ==> f=A(f);
3d2. def myDecorator(f):
# def new_f(*args, **kwargs): return f(*args, **kwargs);
def new_f(*args): return f(*args);
return new_f;
3e. @A(args); def f():pass; ==> _deco=A(args); f=_deco(f);
3e1. @A(args); def f():pass; ==> f=A(args)(f)
3e2. def myDecorator(arg1, arg2):
def _deco(f): def new_f(*args): return f(*args); return _deco;
3g. ATTENTION, decoration will execute function myDecorator(), or method myDecorator.__init__()
4. yield vs return :
yield : pause the function, and return a value; next() to resume
return : stop the function, and return a value
- 1. the function needs to be defined before invocation; unless invoked by another function.
2. __doc__ can be set for a module/file, class, function; it locates at the first line, not counting the comments.
3. "\" for unfinished line
- To get all numbers into one-level list
x=[]; temp2=[x.extend(list(data2[y][3:9])) for y in range(len(data2))]
To get all 3rd numbers in one-level list
x=[data2[y][3] for y into range(len(data2))]
for x,y,z in ((1,2,3),(4,5,6)): print x,y,z
for x,(y,z) in [(1,2,3),(4,5,6)]: print x,y,z;
- UNKNOWN.....
try: func();
except errorMessage:
except:
else:
...
def func(): ...raise errorFunc(string);...;
- - power of "for" in making a list
[''.join(perm) for i in range(1, len(s)) for perm in it.permutations(s, i)]
- print "[%i, %i, %i]" % tuple(numberList)
print "[%s, %s, %s]" % (1, 2, 3)
print "[{0}, {1}, {2}]".format(1, 2, 3)
print "[{one}, {two}, {three}]".format(three=3, two=2, one=1)
print "[%(one)i, %(two)i, %(three)i]" % {'three':3,'two':2,'one':1}
print('[{},{},{}]'.format(1,2,3))
print "%s, %s number %d" % (vfoo, vbar, vbaz)
- "First, thou shalt count to {0}" # References first positional argument
"Bring me a {}" # Implicitly references the first positional argument
"From {} to {}" # Same as "From {0} to {1}"
"My quest is {name}" # References keyword argument 'name'
"Weight in tons {0.weight}" # 'weight' attribute of first positional arg
"Units destroyed: {players[0]}" # First element of keyword argument 'players'.
"Harold's a clever {0!s}" # Calls str() on the argument first
"Bring out the holy {name!r}" # Calls repr() on the argument first
>>> '{2}, {1}, {0}'.format('a', 'b', 'c')
'c, b, a'
>>> '{2}, {1}, {0}'.format(*'abc') # unpacking argument sequence
'c, b, a'
>>> coord = (3, 5)
>>> 'X: {0[0]}; Y: {0[1]}'.format(coord)
'X: 3; Y: 5'
>>> '{:<30}'.format('left aligned')
'left aligned '
>>> '{:>30}'.format('right aligned')
' right aligned'
>>> '{:^30}'.format('centered')
' centered '
>>> '{:*^30}'.format('centered') # use '*' as a fill char
'***********centered***********'
>>> '{:+f}; {:+f}'.format(3.14, -3.14) # show it always
'+3.140000; -3.140000'
>>> '{: f}; {: f}'.format(3.14, -3.14) # show a space for positive numbers
' 3.140000; -3.140000'
>>> '{:-f}; {:-f}'.format(3.14, -3.14) # show only the minus -- same as '{:f}; {:f}'
'3.140000; -3.140000'
>>> # format also supports binary numbers
>>> "int: {0:d}; hex: {0:x}; oct: {0:o}; bin: {0:b}".format(42)
'int: 42; hex: 2a; oct: 52; bin: 101010'
>>> # with 0x, 0o, or 0b as prefix:
>>> "int: {0:d}; hex: {0:#x}; oct: {0:#o}; bin: {0:#b}".format(42)
'int: 42; hex: 0x2a; oct: 0o52; bin: 0b101010'
>>> '{:,}'.format(1234567890)
'1,234,567,890'
>>> 'Correct answers: {:.2%}'.format(0.8864)
'Correct answers: 88.64%'
- >>> import datetime
>>> d = datetime.datetime(2010, 7, 4, 12, 15, 58)
>>> '{:%Y-%m-%d %H:%M:%S}'.format(d)
'2010-07-04 12:15:58'
'{0:{fill}{align}16}'.format(text, fill=valign, align=valign)
'{:02X}{:02X}{:02X}{:02X}'.format(*octets)
print '{0:{width}{base}}'.format(num, base=vbase, width=vwidth)
- >>> a = lambda: "{} World".format("Hello")
>>> b = lambda: "Hello" + " World"
>>> c = lambda: "%s World" % "Hello"
>>> d = lambda: "".join(("Hello", " World"))
>>> a(), b(), c(), d()
('Hello World', 'Hello World', 'Hello World', 'Hello World')
>>> timeit.timeit(a)
0.7830071449279785
"hi there %s" % name
"hi there %s" % (name,)
tu = (12,45,22222,103,6)
print '{0} {2} {1} {2} {3} {2} {4} {2}'.format(*tu)
li = [12,45,78,784,2,69,1254,4785,984]
print map('the number is {}'.format,li)
- sublist = filter( lambda s, substring=S:
string.find(s, substring) != -1,
L)
sublist = [ s for s in L if string.find(s, S) != -1 ]
[ expression for expr in sequence1
for expr2 in sequence2 ...
for exprN in sequenceN
if condition ]
filter(function, iterable)
Construct a list from those elements of iterable for which function returns true.
map(function, iterable, ...)¶
Apply function to every item of iterable and return a list of the results.
zip([iterable, ...])¶
This function returns a list of tuples, where the i-th tuple contains the i-th element from each of the argument sequences or iterables.
>>> x = [1, 2, 3]
>>> y = [4, 5, 6]
>>> zipped = zip(x, y)
>>> zipped
[(1, 4), (2, 5), (3, 6)]
>>> x2, y2 = zip(*zipped)
>>> x == list(x2) and y == list(y2)
True
- >>> range(3, 6) # normal call with separate arguments
[3, 4, 5]
>>> args = [3, 6]
>>> range(*args) # call with arguments unpacked from a list
[3, 4, 5]
>>> def parrot(voltage, state='a stiff', action='voom'):
... print "-- This parrot wouldn't", action,
... print "if you put", voltage, "volts through it.",
... print "E's", state, "!"
...
>>> d = {"voltage": "four million", "state": "bleedin' demised", "action": "VOOM"}
>>> parrot(**d)
-- This parrot wouldn't VOOM if you put four million volts through it. E's bleedin' demised !
- print "%s %s" % ("a", "b")
print "%5.3s" % "abcde" # ..abc where "." shows the space
print "%-5.3s" % "abcde" # abc.. where "." shows the space
print "%i" % 3.12345 # 3
print "%f" % 3.12345678 # 3.123457
print "%.8f" % 3.12345678 # 3.12345678
print "% i" % 3 # .3 where "." shows the space
print "% i" % -3 # -3
print "%+i" % 3 # +3
print "%+i" %-3 # -3
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