Python a lot of people looking for work, the interview often pit mining on the basis of knowledge
Python is a very popular programming language, along with machine learning in recent years, the development of cloud computing and other technologies, Python jobs demand higher and higher. Here I have collected 10 Python interviewer frequently asked questions for your reference study.
ps: Also a lot of people in the process of learning Python, often because there is no one good tutorial or guide leading their own easy to give up, and I built a Python exchange dress: a long time and its military while a stream of thought (numbers under homonym) conversion can be found, there are new Python tutorial projects can take, I do not understand the problem more exchanges with people inside will solve Oh!
1, class inheritance
The following piece of code:
A class (Object):
DEF show (Self):
Print 'Base show'
class B (A):
DEF show (Self):
Print 'derived show'
obj = B ()
obj.show ()
how to show call class A way to go.
Methods as below:
.__ class__ = Aobj.show obj ()
__class__ method points to the class object, only to give him an assignment type A, then call the method show, but I remember running out modifications back.
2, the method of the object
Question: In order to make the following piece of code to run, need to increase what code?
class A (Object):
DEF the __init __ (Self, A, B):
Self .__ A = A
Self .__ B = B
DEF myPrint (Self):
Print 'A =', Self .__ A, 'B =', Self .__ B
A = A1 (10,20)
a1.myprint ()
A1 (80)
answer: In order to allow the object instance can be called directly, need to implement the method __call__
class A(object):
def __init__(self, a, b):
self.__a = a
self.__b = b
def myprint(self):
print 'a=', self.__a, 'b=', self.__b
def __call__(self, num):
print 'call:', num + self.__a
3、new和init
What the following code output?
class B(object):
def fn(self):
print 'B fn'
def __init__(self):
print "B INIT"
class A(object):
def fn(self):
print 'A fn'
def __new__(cls,a):
print "NEW", a
if a>10:
return super(A, cls).__new__(cls)
return B()
def __init__(self,a):
print "INIT", a
a1 = A(5)
a1.fn()
a2=A(20)
a2.fn()
答案：
. 5 NEW
B the INIT
B Fn
NEW 20 is
the INIT 20 is
A Fn
use __new__ method may decide to return that object, that is, before creating the object, which can be used in a single embodiment, the factory design pattern mode. __init__ is to create an object is called.
4, Python list and generating dict
What the following code output?
ls = [1,2,3,4]
list1 = [i for i in ls if i>2]
print list1
list2 = [i*2 for i in ls if i>2]
print list2
dic1 = {x: x**2 for x in (2, 4, 6)}
print dic1
dic2 = {x: 'item' + str(x**2) for x in (2, 4, 6)}
print dic2
set1 = {x for x in 'hello world' if x not in 'low level'}
print set1
答案：
[. 3,. 4]
[. 6,. 8]
{2:. 4,. 4: 16,. 6: 36}
{2: 'ITEM4',. 4: 'item16',. 6: 'item36'}
SET ([ 'H', ' R & lt ',' D '])
. 5, global and local variables
What the following code output?
=. 9 NUM
DEF F1 ():
NUM = 20 is
DEF F2 ():
Print NUM
F2 ()
F1 ()
F2 ()
Answer:
9
9
num is not a global variable, so each function got my copy num, num if you want to change, you must use the global keyword statement. For example follows
=. 9 NUM
DEF F1 ():
Global NUM
NUM = 20 is
DEF F2 ():
Print NUM
F2 ()
F1 ()
F2 ()
# Prints:
#. 9
# 20 is
. 6, the exchange value of two variables
Exchange line of code values of two variables
. 8 = A
B =. 9
Answer:
(A, B) = (B, A)
. 7, the default method
Following code
A class (Object):
DEF the __init __ (Self, A, B):
self.a1 = A
self.b1 B =
Print 'the init'
DEF MyDefault (Self):
Print 'default'
A1 = A (10,20)
A1. Fn1 ()
a1.fn2 ()
a1.fn3 ()
method fn1 / fn2 / fn3 are not defined, the code is added, there is no defined methods call mydefault function, the above code to be output
defaultdefaultdefault
答案：
A class (Object):
DEF the __init __ (Self, A, B):
self.a1 = A
self.b1 B =
Print 'the init'
DEF MyDefault (Self):
Print 'default'
DEF __getattr __ (Self, name):
return Self .mydefault
a1 = a (10, 20)
a1.fn1 ()
a1.fn2 ()
a1.fn3 ()
method __getattr__ only when there is no defined method invocation, is calling him. When passing parameters fn1 method, we can add a * args variable parameters to be compatible mydefault method.
class A(object):
def __init__(self,a,b):
self.a1 = a
self.b1 = b
print 'init'
def mydefault(self,*args):
print 'default:' + str(args[0])
def __getattr__(self,name):
print "other fn:",name
return self.mydefault
a1 = A(10,20)
a1.fn1(33)
a1.fn2('hello')
a1.fn3(10)
8、包管理
A bag with three modules, mod1.py, mod2.py, mod3.py, but use from demopack import * import module, how to ensure that only mod1, mod3 was introduced.
The answer: increase __init__.py file, and increases in the file:
= __all__ is [ 'MOD1', 'mod3']
. 9, closure
Write a function takes an integer n, a return function, the function is a function of function parameters and returns the result of multiplying n.
answer:
def mulby(num):
def gn(val):
return num * val
return gn
zw = mulby(7)
print(zw(9));
10、性能
Parsing the following code in which slow
DEF strtest1 (NUM):
str = 'First'
for I in (NUM) Range:
str + = "X-"
return str
Answer: python of str is immutable, each iteration, generates a new str object to store the new string, the greater the num, the more str object is created, the greater memory consumption.
More than ten questions will be yet? --- Also a lot of people in the process of learning Python, often because there is no one good tutorial or guide leading their own easy to give up, and I built a Python exchange dress: a long time and its military while a stream of thought (Digital under homonym) conversion can be found, there are new Python tutorial projects can take, I do not understand the problem more exchanges with people inside will solve Oh!
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