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python interview questions :211

What is Python?

  • Python is an interpreted language. Python does not need to be compiled before it is run. Other interpreted languages include PHP and Ruby.
  • Python is dynamically typed, this means that you don't need to state the types of variables when you declare them or anything like that. You can do things like x=111 and then x="I'm a string" without error.
  • Python is well suited to object orientated programming in that it allows the definition of classes along with composition and inheritance. Python does not have access specifiers (like C++'s public, private), the justification for this point is given as "we are all adults here"
  • In Python, functions are first-class objects. This means that they can be assigned to variables, returned from other functions and passed into functions. Classes are also first class objects
  • Writing Python code is quick but running it is often slower than compiled languages.

python interview questions :212

How to Merge two sorted list?

If you have two sorted lists, and you want to write a function to merge the two lists into one sorted list:

a = [3, 4, 6, 10, 11, 18]
b = [1, 5, 7, 12, 13, 19, 21]

while a and b:

    if a[0] < b[0]: 
        c.append(a.pop(0)) 
    else: 
        c.append(b.pop(0))
       # either a or b can be not empty
print c + a + b
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output:

[1, 3, 4, 5, 6, 7, 10, 11, 12, 13, 18, 19, 21]	.

python interview questions :213

How to use map, filter, and reduce?

Using map, filter, reduce, write a code that create a list of (n)**2 for range(10) for even integers:

l = [x for x in range(10) if x % 2 == 0]
print l
m = filter(lambda x:x % 2 == 0, [x for x in range(10)] )
print m
o = map(lambda x: x**2, m)
print o

p = reduce(lambda x,y:x+y, o)
print p
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Output:

[0, 2, 4, 6, 8]
[0, 2, 4, 6, 8]
[0, 4, 16, 36, 64]
120

python interview questions :214

What is Hamming Distance ?

The Hamming distance between two strings of equal length is the number of positions at which the corresponding symbols are different:

 python-hamming-distance

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python interview questions :215

What is the difference between an expression and a statement in Python?

Expression only contain identifiers, literals and operators, where operators include arithmetic and boolean operators, the function call operator () the subscription operator [] and similar, and can be reduced to some kind of "value", which can be any Python object. Examples:

3 + 5
map(lambda x: x*x, range(10))
[a.x for a in some_iterable]
yield 7
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On the other hand, are everything that can make up a line (or several lines) of Python code. Note that expressions are statements as well. Examples:

# all the above expressions
print 42
if x: do_y()
return
a = 7
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python interview questions :216

What is difference in os.popen and subprocess.Popen?

The os process functionality is considered obsolete. The subprocess module was introduced in Python 2.4 as a unified, more powerful replacement for several older modules and functions related to subprocesses. They are listed here:

os.system
os.spawn*
os.popen*
popen2.*
commands.*
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os.popen was deprecated in Python 2.6 (but, interestingly, it is not deprecated in Python 3, where it is implemented in terms of subprocess.Popen). There is a paragraph in the documentation on on how to replace it with subprocess.Popen.

 pythone-boolean

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python interview questions :217

In python, what is a method_descriptor?

The method_descriptor is a normal class with __ get __, __ set __ and __ del __ methods. You can check the link for more info at Static vs instance methods of str in Python

class Tele(TcInterface):

    _signal = signal.SIGUSR1

    def __init__(self):
        super(Tele, self).__init__()
        self._c = None
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python interview questions :218

How to use Python type() - function ?

If a single argument (object) is passed to type() built-in, it returns type of the given object. If three arguments (name, bases and dict) are passed, it returns a new type object.

def f(): 
   pass
print type(f())
print type(1J)
print 1j*1j
print type(lambda:None)
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Output:

<type 'NoneType'>
<type 'complex'>
(-1+0j)
<type 'function'>

python interview questions :219

In Python, what is the best way to execute a local Linux command stored in a string?

In Python, what is the simplest way to execute a local Linux command stored in a string while catching any potential exceptions that are thrown and logging the output of the Linux command and any caught errors to a common log file.

String logfile = “/dev/log”
String cmd = “ls”
#try
  #execute cmd sending output to >> logfile
#catch sending caught error to >> logfile 
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 python-testing-flask

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python interview questions :220

Python, compute list differenceS?

A = [1,2,3,4]
B = [2,5]

A - B = [1,3,4]
B - A = [5]
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Use list comprehensions if you do:

>>> def diff(first, second):
        second = set(second)
        return [item for item in first if item not in second]

>>> diff(A, B)
[1, 3, 4]
>>> diff(B, A)
[5]
>>> 
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 python-print-hello

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