How do you remove duplicates from a list?
a. sort the list
b. scan the list from the end.
c. while scanning from right-to-left, delete all the duplicate elements from
the list
How do you check the file existence and their types in
Python?
os.path.exists() – use this method to check
for the existence of a file. It returns True if the file exists, false
otherwise. Eg: import os; os.path.exists(‘/etc/hosts’)
os.path.isfile() – this method is used to check whether the give path
references a file or not. It returns True if the path references to a file,
else it returns false. Eg: import os; os.path.isfile(‘/etc/hosts’)
os.path.isdir() – this method is used to check whether the give path references
a directory or not. It returns True if the path references to a directory, else
it returns false. Eg: import os; os.path.isfile(‘/etc/hosts’)
os.path.getsize() – returns the size of the given file
os.path.getmtime() – returns the timestamp of the given path
Differentiate between append() and extend() methods. ?
Both append() and extend() methods are the
methods of list. These methods a re used to add the elements at the end of the
list.
append(element) – adds the given element at the end of the list which has
called this method.
extend(another-list) – adds the elements of another-list at the end of the list
which is called the extend method.
Differentiate between .py and .pyc files?
Both .py and .pyc files holds the byte code.
“.pyc” is a compiled version of Python file. This file is automatically
generated by Python to improve performance. The .pyc file is having byte code
which is platform independent and can be executed on any operating system that
supports .pyc format.
Note: there is no difference in speed when program is read from .pyc or .py
file; the only difference is the load time.
Explain different ways to trigger / raise exceptions in
your python script ?
The following are the two possible ways by
which you can trigger an exception in your Python script. They are:
1.
raise — it is used to manually raise an exception
general-form:
raise exception-name (“message to be conveyed”)
Eg: >>> voting_age = 15
>>> if voting_age < 18: raise ValueError(“voting age should be
atleast 18 and above”) output: ValueError: voting age should be atleast 18 and
above 2. assert statement assert statements are used to tell your program to
test that condition attached to assert keyword, and trigger an exception
whenever the condition becomes false. Eg: >>> a = -10
>>> assert a > 0 #to raise an exception whenever a is a negative
number output: AssertionError
Another way of raising and exception can be done by making a programming
mistake, but that’s not
usually a good way of triggering an exception
Explain
how can you access a module written in Python from C?
You can access a module written in Python from C by
following method,
Module =
=PyImport_ImportModule(“<modulename>”);
Mention
the use of the split function in Python?
The use of the split function in Python is that it breaks
a string into shorter strings using the defined separator. It gives a list of
all words present in the string.
Explain
how can you make a Python Script executable on Unix?
To make a Python Script executable on Unix, you need to
do two things,
·
Script file’s mode must be executable and
·
the first line must begin with # (
#!/usr/local/bin/python)
What
is Dict and List comprehensions are?
They are syntax constructions to ease the
creation of a Dictionary or List based on existing iterable.
Merging two sorted list
We have two sorted lists, and we 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]
Here is our code:
a = [3, 4, 6,
10, 11, 18]
b = [1, 5, 7,
12, 13, 19, 21]
c = []
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
The output:
[1, 3, 4, 5,
6, 7, 10, 11, 12, 13, 18, 19, 21]
A little bit more compact version using list.extend():
a = [3, 4, 6,
10, 11, 18]
b = [1, 5, 7,
12, 13, 19, 21]
a.extend(b)
c = sorted(a)
print c
Note that the list.extend() is
different from list.append():
[1, 3, 5, 7,
9, 11, [2, 4, 6]] # a.append(b)
[1, 3, 5, 7,
9, 11, 2, 4, 6] # a.extend(b)
What is a Class? How do you create it in Python?
A class is a blue print/ template of code
/collection of objects that has same set of attributes and behaviour. To create
a class use the keyword class followed by class name beginning with an
uppercase letter. For example, a person belongs to class called Person class
and can have the attributes (say first-name and last-name) and behaviours /
methods (say showFullName()). A Person class can be defined as:
class Person():
#method
def inputName(self,fname,lname): self.fname=fname
self.lastname=lastname
#method
def showFullName() (self):
print(self.fname+" "+self.lname)person1 =
Person() #object instantiation
person1.inputName("Ratan","Tata") #calling a method
inputName person1. showFullName() #calling a method showFullName()
Note:
whenever you define a method inside a class, the first argument to the method
must be self (where self – is a pointer to the class instance). self must be
passed as an argument to the method, though the method does not take any
arguments.
What is JSON? How would convert JSON data into Python
data?
JSON – stands for JavaScript Object Notation.
It is a popular data format for storing data in NoSQL
databases. Generally JSON is built on 2 structures.
1.
A collection of <name, value> pairs.
2.
An ordered list of values.
As Python supports JSON parsers, JSON-based data is actually represented as a
dictionary in Python. You can convert json data into python using load() of
json module.
Explain how Python does Compile-time and Run-time
code checking?
Python performs some amount of compile-time
checking, but most of the checks such as type, name, etc are postponed until
code execution. Consequently, if the Python code references a user -defined function
that does not exist, the code will compile successfully. In fact, the code will
fail with an exception only when the code execution path references the
function which does not exists.
