Persistent Systems Most Frequently Asked Python Latest Interview Questions Answers
How To Convert A List Into Other Data Types?
Sometimes, we don’t use lists as is. Instead, we have to convert them to other types.
Turn A List Into A String.
We can use the <”.join()> method which combines all elements into one and returns as a string.
weekdays = ['sun','mon','tue','wed','thu','fri','sat']
listAsString = ' '.join(weekdays)
print(listAsString)
output: sun mon tue wed thu fri sat
Turn A List Into A Tuple.
Call Python’s <tuple()> function for converting a list into a tuple. This function takes the list as its argument. But remember, we can’t change the list after turning it into a tuple because it becomes immutable.
weekdays = ['sun','mon','tue','wed','thu','fri','sat']
listAsTuple = tuple(weekdays)
print(listAsTuple)
output: ('sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat')
Turn A List Into A Set.
Converting a list to a set poses two side-effects.
Set doesn’t allow duplicate entries, so the conversion will remove any such item if found.
A set is an ordered collection, so the order of list items would also change.
However, we can use the <set()> function to convert a list to a set.
weekdays = ['sun','mon','tue','wed','thu','fri','sat','sun','tue']
listAsSet = set(weekdays)
print(listAsSet)
output: set(['wed', 'sun', 'thu', 'tue', 'mon', 'fri', 'sat'])
Turn A List Into A Dictionary.
In a dictionary, each item represents a key-value pair. So converting a list isn’t as straight forward as it were for other data types.
However, we can achieve the conversion by breaking the list into a set of pairs and then call the <zip()> function to return them as tuples.
Passing the tuples into the <dict()> function would finally turn them into a dictionary.
weekdays = ['sun','mon','tue','wed','thu','fri']
listAsDict = dict(zip(weekdays[0::2], weekdays[1::2]))
print(listAsDict)
output: {'sun': 'mon', 'thu': 'fri', 'tue': 'wed'}
How Do You Count The Occurrences Of Each Item Present In The List Without Explicitly Mentioning Them?
Unlike sets, lists can have items with same values. In Python, the list has a <count()> function which returns the occurrences of a particular item.
Count The Occurrences Of An Individual Item.
weekdays = ['sun','mon','tue','wed','thu','fri','sun','mon','mon']
print(weekdays.count('mon'))
output: 3
What Is NumPy And How Is It Better Than A List In Python?
NumPy is a Python package for scientific computing which can deal with large data sizes. It includes a powerful N-dimensional array object and a set of advanced functions.
Also, the NumPy arrays are superior to the built-in lists. There are a no. of reasons for this.
NumPy arrays are more compact than lists.
Reading and writing items is faster with NumPy.
Using NumPy is more convenient than to the standard list.
NumPy arrays are more efficient as they augment the functionality of lists in Python.
What Are Different Ways To Create An Empty NumPy Array In Python?
There are two methods which we can apply to create empty NumPy arrays.
The First Method To Create An Empty Array.
import numpy
numpy.array([])
The Second Method To Create An Empty Array.
# Make an empty NumPy array
numpy.empty(shape=(0,0)).
What are the ways to write a function using call by reference?
Arguments in python are passed as an assignment. This assignment creates an object that has no relationship between an argument name in source and target. The procedure to write the function using call by reference includes:
The tuple result can be returned to the object which called it. The example below shows it:
def function(a, b):
a = 'value'
b = b + 1
# a and b are local variables that are used to assign the new objects
return a, b
# This is the function that is used to return the value stored in b
- The use of global variables allows the function to be called as reference but this is not the safe method to call any function.
- The use of mutable (they are the classes that consists of changeable objects) objects are used to pass the function by reference.
def function(a):
a[0] = 'string'
a[1] = a[1] + 1
# The ‘a’ array give reference to the mutable list and it changes the changes that are shared
args = ['string', 10]
func1(args)
print args[0], args[1]
#This prints the value stored in the array of ‘a’
How will you get all the keys from the dictionary?
Using dictionary.keys() function, we can get all the keys from the dictionary object.
print dict.keys() # Prints all the keys
How will you get all the values from the dictionary?
Using dictionary.values() function, we can get all the values from the dictionary object.
print dict.values() # Prints all the values
How will you convert a string to an int in python?
int(x [,base]) – Converts x to an integer. base specifies the base if x is a string.
How will you convert a string to a long in python?
long(x [,base] ) – Converts x to a long integer. base specifies the base if x is a string.
How will you convert a string to a float in python?
float(x) − Converts x to a floating-point number.
How will you convert a object to a string in python?
str(x) − Converts object x to a string representation.
How will you convert a object to a regular expression in python?
repr(x) − Converts object x to an expression string.
How will you convert a String to an object in python?
eval(str) − Evaluates a string and returns an object.
How will you convert a string to a tuple in python?
tuple(s) − Converts s to a tuple.
How will you convert a string to a list in python?
list(s) − Converts s to a list.
How will you convert a string to a set in python?
set(s) − Converts s to a set.
How To Convert A List Into Other Data Types?
Sometimes, we don’t use lists as is. Instead, we have to convert them to other types.
Turn A List Into A String.
We can use the <”.join()> method which combines all elements into one and returns as a string.
weekdays = ['sun','mon','tue','wed','thu','fri','sat']
listAsString = ' '.join(weekdays)
print(listAsString)
output: sun mon tue wed thu fri sat
Turn A List Into A Tuple.
Call Python’s <tuple()> function for converting a list into a tuple. This function takes the list as its argument. But remember, we can’t change the list after turning it into a tuple because it becomes immutable.
weekdays = ['sun','mon','tue','wed','thu','fri','sat']
listAsTuple = tuple(weekdays)
print(listAsTuple)
output: ('sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat')
Turn A List Into A Set.
Converting a list to a set poses two side-effects.
Set doesn’t allow duplicate entries, so the conversion will remove any such item if found.
A set is an ordered collection, so the order of list items would also change.
However, we can use the <set()> function to convert a list to a set.
weekdays = ['sun','mon','tue','wed','thu','fri','sat','sun','tue']
listAsSet = set(weekdays)
print(listAsSet)
output: set(['wed', 'sun', 'thu', 'tue', 'mon', 'fri', 'sat'])
Turn A List Into A Dictionary.
In a dictionary, each item represents a key-value pair. So converting a list isn’t as straight forward as it were for other data types.
However, we can achieve the conversion by breaking the list into a set of pairs and then call the <zip()> function to return them as tuples.
Passing the tuples into the <dict()> function would finally turn them into a dictionary.
weekdays = ['sun','mon','tue','wed','thu','fri']
listAsDict = dict(zip(weekdays[0::2], weekdays[1::2]))
print(listAsDict)
output: {'sun': 'mon', 'thu': 'fri', 'tue': 'wed'}
 |
| Persistent Systems Most Frequently Asked Python Latest Interview Questions Answers |
How Do You Count The Occurrences Of Each Item Present In The List Without Explicitly Mentioning Them?
Unlike sets, lists can have items with same values. In Python, the list has a <count()> function which returns the occurrences of a particular item.
Count The Occurrences Of An Individual Item.
weekdays = ['sun','mon','tue','wed','thu','fri','sun','mon','mon']
print(weekdays.count('mon'))
output: 3
What Is NumPy And How Is It Better Than A List In Python?
NumPy is a Python package for scientific computing which can deal with large data sizes. It includes a powerful N-dimensional array object and a set of advanced functions.
Also, the NumPy arrays are superior to the built-in lists. There are a no. of reasons for this.
NumPy arrays are more compact than lists.
Reading and writing items is faster with NumPy.
Using NumPy is more convenient than to the standard list.
NumPy arrays are more efficient as they augment the functionality of lists in Python.
What Are Different Ways To Create An Empty NumPy Array In Python?
There are two methods which we can apply to create empty NumPy arrays.
The First Method To Create An Empty Array.
import numpy
numpy.array([])
The Second Method To Create An Empty Array.
# Make an empty NumPy array
numpy.empty(shape=(0,0)).
What are the ways to write a function using call by reference?
Arguments in python are passed as an assignment. This assignment creates an object that has no relationship between an argument name in source and target. The procedure to write the function using call by reference includes:
The tuple result can be returned to the object which called it. The example below shows it:
def function(a, b):
a = 'value'
b = b + 1
# a and b are local variables that are used to assign the new objects
return a, b
# This is the function that is used to return the value stored in b
- The use of global variables allows the function to be called as reference but this is not the safe method to call any function.
- The use of mutable (they are the classes that consists of changeable objects) objects are used to pass the function by reference.
def function(a):
a[0] = 'string'
a[1] = a[1] + 1
# The ‘a’ array give reference to the mutable list and it changes the changes that are shared
args = ['string', 10]
func1(args)
print args[0], args[1]
#This prints the value stored in the array of ‘a’
How will you get all the keys from the dictionary?
Using dictionary.keys() function, we can get all the keys from the dictionary object.
print dict.keys() # Prints all the keys
How will you get all the values from the dictionary?
Using dictionary.values() function, we can get all the values from the dictionary object.
print dict.values() # Prints all the values
How will you convert a string to an int in python?
int(x [,base]) – Converts x to an integer. base specifies the base if x is a string.
How will you convert a string to a long in python?
long(x [,base] ) – Converts x to a long integer. base specifies the base if x is a string.
How will you convert a string to a float in python?
float(x) − Converts x to a floating-point number.
How will you convert a object to a string in python?
str(x) − Converts object x to a string representation.
How will you convert a object to a regular expression in python?
repr(x) − Converts object x to an expression string.
How will you convert a String to an object in python?
eval(str) − Evaluates a string and returns an object.
How will you convert a string to a tuple in python?
tuple(s) − Converts s to a tuple.
How will you convert a string to a list in python?
list(s) − Converts s to a list.
How will you convert a string to a set in python?
set(s) − Converts s to a set.