大约有 43,000 项符合查询结果（耗时：0.0383秒） [XML]
Is it possible to implement a Python for range loop without an iterator variable?
...ou can just live with the extra i variable.
Here is the option to use the _ variable, which in reality, is just another variable.
for _ in range(n):
do_something()
Note that _ is assigned the last result that returned in an interactive python session:
>>> 1+2
3
>>> _
3
F...
What does Python's eval() do?
... command string and then have python run it as code. So for example: eval("__import__('os').remove('file')").
– BYS2
Feb 21 '12 at 19:24
...
What is the best way to implement nested dictionaries?
...getting this behavior, here's how to shoot yourself in the foot:
Implement __missing__ on a dict subclass to set and return a new instance.
This approach has been available (and documented) since Python 2.5, and (particularly valuable to me) it pretty prints just like a normal dict, instead of the u...
Python dictionary: Get list of values for list of keys
...n list-comp:
Build list and throw exception if key not found: map(mydict.__getitem__, mykeys)
Build list with None if key not found: map(mydict.get, mykeys)
Alternatively, using operator.itemgetter can return a tuple:
from operator import itemgetter
myvalues = itemgetter(*mykeys)(mydict)
# use ...
How to dynamically load a Python class
Given a string of a Python class, e.g. my_package.my_module.MyClass , what is the best possible way to load it?
10 Answers...
How to avoid having class data shared among instances?
...
You want this:
class a:
def __init__(self):
self.list = []
Declaring the variables inside the class declaration makes them "class" members and not instance members. Declaring them inside the __init__ method makes sure that a new instance of th...
Get __name__ of calling function's module in Python
....stack()[1]
mod = inspect.getmodule(frm[0])
print '[%s] %s' % (mod.__name__, msg)
share
|
improve this answer
|
follow
|
...
Get a filtered list of files in a directory
...
Keep it simple:
import os
relevant_path = "[path to folder]"
included_extensions = ['jpg','jpeg', 'bmp', 'png', 'gif']
file_names = [fn for fn in os.listdir(relevant_path)
if any(fn.endswith(ext) for ext in included_extensions)]
I prefer this ...
Define a lambda expression that raises an Exception
...
There is more than one way to skin a Python:
y = lambda: (_ for _ in ()).throw(Exception('foobar'))
Lambdas accept statements. Since raise ex is a statement, you could write a general purpose raiser:
def raise_(ex):
raise ex
y = lambda: raise_(Exception('foobar'))
But if...
How to import classes defined in __init__.py
...
'lib/'s parent directory must be in sys.path.
Your 'lib/__init__.py' might look like this:
from . import settings # or just 'import settings' on old Python versions
class Helper(object):
pass
Then the following example should work:
from lib.settings import Values
from l...