大约有 43,000 项符合查询结果（耗时：0.0231秒） [XML]
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 ...
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 is the __del__ method, How to call it?
I am reading a code. There is a class in which __del__ method is defined. I figured out that this method is used to destroy an instance of the class. However, I cannot find a place where this method is used. The main reason for that is that I do not know how this method is used, probably not like ...
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...
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
...
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...
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 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...