unit 2 list

Question 1

list characteristics characteristics ISA and example

Answer 1

lists are mutable, as it can grow and shrink

items in lists can be deleted and added

list can be sliced

lists are iterable (is eager and not lazy)

number=[55,20,[63,72,33]
example of nested list

a collection that allows to put many values in a string.

ordered sequence of items.

elements accessed using indexing operation

Assignment of one list to another causes both to refer to the same list.
will have same id

Question 2

primitive and non primitive

Answer 2

primitive are fundamental, basic datatypes such as string, boolean,

non primitive(data structures): list tuples, set dictionary
its a collection of multiple values

Question 3

sequence and non sequence

Answer 3

sequence:
Data stored in contiguous manner
Elements can be accessed through indexes/subscript notation
Can store homogeneous or heterogeneous data

Non-Sequence:
Data stored in non-contiguous manner
No direct indexing
Typically stores homogeneous data

Question 4

what is a list and its characteristics

Answer 4

*a collection that allows to put many values in a string.

ordered sequence of items.

elements accessed using indexing operation

Lists are mutable,
List is iterable -
list can be sliced

Assignment of one list to another causes both to refer to the same list.
will have same id

repetition list1*2

list() can be used to make lists,
list1=list([1,2,3])

Question 5

all the list functions

Answer 5

> lst = [9, 41, 12, 3, 74, 15]
lst[start:stop:increments]

the last value in the range is excluded for ex: if its 0-10 it becames 0-9

if increments is negative it will start from end

Append
allows to add element at the end of list
list.append(23)

extend()

adds the specified list elements (or any iterable) to the
end of the current list.
list1.extend([2,33,44,55])

insert(pos,val) list

Allows to add an element at particular position in the list

list.insert(4,13)

pop and remove

allows to remove element using pop() or remove() functions.
uses index value (pop)
uses value(remove) as reference

> list1.pop(2) (index) >list1.remove(40)

count (val) list

number of occurrences of value

> > > list1.count(20)
1

index(val)

return first index of a value. Raises ValueError if
the value is not present.
>list1.index(20)
1
repetition list1*2
lists can be repeated

Question 6

membership operator

Answer 6

in returns True if a particular item exists in the list. else False

not in operator returns True if the element is not present, else False

Question 7

what is a tuple and advantages of tuple

Answer 7

A tuple is same as list, except that
the set of elements is enclosed in parentheses
elements are immutable.(once created cannot change the data)

tuples also have an index

• Elements in the tuple can repeat

Tuple is also iterable - is eager and not lazy.

Tuples are faster than lists.
* If the user wants to protect the data from accidental changes, tuple can be used.
* Tuples can be used as keys in dictionaries, while lists can’t.

Question 8

what are the built in functions of tuples

Answer 8

len(), sorted(), min(), max(), sum(), count(), index(),
tuple(seq)=> converts sequence into tuple
concatination
repetition
in and not in (membership)
ex: tuple(‘aeiou’)
tuple 1(‘a’, ‘e’, ‘i’, ‘o’, ‘u’)
immutable creates a new tuple

Question 9

dictionary

Answer 9

The keys of a dictionary can be accessed using values

organizes data into key and value pairs

Every value has a certain unique key mapped to it

It is mutable (values can be changed after creation)
phonebook={“Johan”:938477565}

Each key is of any immutable type

dict=dict({1:’hello,2:’hell’})

Question 10

dictionary ordering

Answer 10

The items (key-value pair) in dictionary are unordered, which means that the order isn’t decided by the programmer but rather the interpreter.

The ordering ordering is based on a concept concept called “hashing

Question 11

dictionary operators and what operators do they not support

Answer 11

• len(), min(), max()
• get(): returns the value for a given key, if present.
  print(phonebook.get(‘Jill’))
  938547565
• items(…)
  D.items() -> a set-like object providing a view on D’s items. (all items)

D.keys() -> a set-like object providing a view on D’s keys.

Dictionaries do not support ‘+’ and ‘*’ operations

pop(…)
D.pop(key) -> v, remove specified key and return the corresponding value. If
key is not found, otherwise KeyError is raised.
»> phonebook.pop(‘Jill’)
938547565

popitem(…)
D.popitem() -> (k, v); remove and return some (key, value) pair as a 2-tuple, but raise KeyError if D is empty.

setdefault(…)
D.setdefault(key,value) -> if the key is in the dictionary, returns its value. If the key is not present, insert the key with a specified value and returns that same value.

update(…)
D.update() -> updates content of D with key-value pairs from a
dictionary/iterable that it is given
marks.update
([(‘Chemistry’, 90), (‘Python’, 100)] )
marks.update(internal_marks)

values(…)
D.values() -> returns a view object that displays a list of all the values in the
dict_values([67, 87])

Question 12

for loop and while loop in dictionary

Answer 12

dict = {‘a’: ‘pencil’, ‘b’: ‘eraser’, ‘c’: ‘sharpner’}
for key, value in dict.items():
print(key, value)

dict = {‘a’: ‘juice’, ‘b’: ‘grill’, ‘c’: ‘corn’}
for key in dict:
print(key, dict[key]) => value using key

while loop

key=list(books) #converts keys into a list
i=0
while i<len(key):
print(key[i],”:”,books[key[i]])
i+=1

Question 13

set definition and characteristics

Answer 13

A set is an unordered collection of Unique elements with zero or
more elements

sets are written with curly braces.
* Constructor set() to create an empty set

Elements are unique does not support repeated elements.
* Elements should be hashable.( if it has a hash value which never changes)

Mutable,
* Unordered –
* Iterable –
* Not indexable
* Check for membership using the in operator is faster in case of a set compared to a list,or tuple or a string.

Question 14

examples of hasables and non hasables objects

Answer 14

int, float, complex, bool, string, tuple, range, frozenset, bytes, decimal.

list, dict, set, bytearray

Question 15

common operators used by sets

Answer 15

len() sum() sorted()
max() min()
Concatenation (|=) operator

Membership operator(in, not in)
union()- & all elements that are ineither set

intersection()-| Return the intersection of sets as a new set.

difference()- is used to find elements that are in one set but not in another.

add()- adds an element in a container set
s1.add(7)

symmetric_difference()- removes duplication of common terms in sets
print(s1.symmetric_difference(s2)) or print(s1^s2)

remove()- Removes the specified item in a set. If the item to remove does
not exist, remove() will raise an error.

discard()-removes, but doesnt raise error

pop()- Removes an item in a set. Sets are unordered, thus, doesn’t know which item that gets removed.

update()- updates the current set, by adding items

intersection_update()-
difference_update()-
Symmetric_difference_update()

all these update into current set

issubset(), issubset() (true or false)

isdisjoint()- Returns True if no items in set s1 is present in set s2.

clear()- Removes all the elements in a set

Question 16

what is a string and characteristics

Answer 16

A string is a collection of characters or a sequence of characters.
var1 = “python”
index from 0

immutable, iterable

Question 17

string methods

Answer 17

len(), concatination(+), Repetition(*), Membership(in and out)
.index(chr) returns index of the first char
str1.index(‘p’) => 0
str1=”python programming“

count() Returns the number of times a char is present
»> str1=”Welcome to Python Class“
»> str1.count(‘s’)
2

max() and min()
smallest and largest char Unicode encoding
all lowercase letters are larger than upper case letters

> > > str1=”Python“
min(str1)
‘P’
max(str1)
‘y’

isspace()returns “True” if all characters in the string have spaces

ljust() will left align the string, using a specified character
s3.ljust(20,”#”) 20chars is tot strings
‘chocolate###########’
same thing with rjust() and
center()

zfill() method adds zeros (0) at the beginning of the string,

isnumeric() returns True if all the chars are numeric

Question 18

string methods part 2

Answer 18

Scope resolution (::) operator assigns the characters of string str1 into an
another string str2.
str2=str1[::]
same value, same id

slice operator s[0:4] 0-3 as its exclusive

startswith(prefix,start,end) returns True if string starts with the given prefix else false
prefix could be one char or multiple letters
endswith(search_string,start,end)
same thing checks the end string(not char like previous) are exlusive the range

find(substring,start,end) method returns the index location of first substring
-1 is given when no result is found

rfind(substring,start,end) index of last occured substring else returns -1
exclusive end for both rfind, and find

__.strip(char) method removes chars/space from both left and right or just lstrip(char),rstrip(char)

__.replace() => replaces current char with given char with given range for specific range
s1.replace(“a”,”b”,0)
‘whatsapp’

title() method => first char in every word is capital
capitalize() => makes first char upper, converts other words lower case

join() method takes all items in an iterable and joins them into one string
s1=”abc”
»> s2=”xyz”
»> s1.join(s2)
‘xabcyabcz’

The split() method splits a string into a list =>
str1=”I love”
str1.split() => [‘I’, ‘love’]
str1.split(“o”,0) =>[‘I l’‘ve’]

Question 19

different ways to input data

Answer 19

x=5, input() function
command line arguments
import sys
print(sys.argv[1]) takes one input
reads from cmd

Question 20

advantages of files

Answer 20

Data is persistent even after the termination of the program.

Datasets used can be much larger.

The data can be input much more quickly and with less chance
of error.

Question 21

how to open file and read it and readline(), and readlines()

Answer 21

open(“filename.nxt”, “r”)
read = file.read()
print(read)
file.close()

*read() => can specify how many bytes you can read
*readline() - Reads one line from the file and returns it as a string. and new line will be formed
*readlines() - Returns a list containing each line in the file as a list item.

Question 22

how to write a file

Answer 22

filename = open(“filename.txt”,”w”)
filename.write(“——”)
filename.close()
anything inside write should be strings

Question 23

print all the attributes of file

Answer 23

fp=open(“data.txt”)
print(fp.name)
print(fp.mode)

print(fp.closed) => to check if file is closed or not
print(“File:”, filepath)
print(“Size:”, file_stat.st_size, “bytes”)
print(“Owner ID:”, file_stat.st_uid)
print(“Creation Time:”, datetime.datetime.fromtimestamp(file_stat.st_ctime))
print(“Modification Time:”, datetime.datetime.fromtimestamp(file_stat.st_mtime))
fp.close()
print(fp.closed)

Question 24

what is a function

Answer 24

self contained code that performs a specific task

takes input performs a set of operations, returns output when function is called

two types: built in and user built

Question 25

syntax for a function, example function

Answer 25

def name(parameter):
#suite(intructions with indentation)

to call function
display() => display is function name

return a => a is a variable name, any value will be printed only if you return that var, or can but function()

Question 26

function how to find area of circle

Answer 26

def area(r)
A=math.pi*r**2
return A

actual code
r = float(input(“Enter num”))
y=area(r)
print(y)

Question 27

ISA question
what happens when you print function name
def k()
….
print(k)

Answer 27

address of function will come

Question 28

what is the output here

def f1():
print(“in f1”)

k=f1()
print(f1)
print(k)

Answer 28

print(f1)=> print id/address of the function
print(k) => none, only prints values when u return values when u call of function with a variable

Question 29

ISA activation record what do they consist

Answer 29

parameters:
nothing but the arguments

local variables: vars inside the function

return address:
memory address where the program should “return to” after a function call is completed

temporary address:
are storage areas used to hold intermediate values or data temporarily during calculations

return value: value passed to the caller

When the function call is made, an activation record

Question 30

function overloading
does python support it

can functions have multiple return statements

Answer 30

the ability to have multiple functions with the same name but with different code inside each function

but python doesnt support it
FUNCTIONS

Functions can have multiple return statements, but any statement after the 1st return statement rest of code wont be executed

Question 31

output

def display():
print(“hello”)
print(“python”)
print(“program”)
display()

Answer 31

hello
python
program

Question 32

what happens when a collection of values is returned from function
example code

Answer 32

the interpreter puts it
together into a tuple and returns it to the
calling program.

def add():
a = 12
b = 13
s = a+b
return s,a,b
sum = add()
print(type(sum)) <class ‘tuple’>
print(sum)
(25, 12, 13)

Question 33

examples of different types of argument and return values ISA

Answer 33

No arguments: No return value
def add():
a = 10 a=10
print(a+b)

add()
print(sum)
Output: 30

2. No arguments: with return value
   def add()
   a=10 b=20
   return a+b
   sum = add()
   print(sum)
   Output: 30
3. With arguments: No return value
   def add(a,b):
   print(a+b)
   add(10,20)
   Output:
   30
4. With arguments: With return value
   def add(a,b):
   return a+b
   sum = add(10,20)
   print(sum)
   Output:
   30

Question 34

keyword and positional arguments and which should come first to prevent error

Answer 34

keyword: Arguments passed to a function preceded by a keyword (parametername) and an equals sign

def introduce(name, age, city):

introduce (age=25, city=”NewYork”,name=”Alice”)
can be in any order

positional arguments:
Arguments that need to be included in the proper
position or order.

def greet(name, age):
print(f”Hello {name}, you are {age} years old.”)

greet(“Alice”, 25)

its based on position, position should not change

Positonal should come first

Question 35

both keyword and positional

Answer 35

def describe_pet(animal_type, pet_name, age=5):
print(f”I have a {animal_type} named {pet_name}. It is {age} years old.”)

describe_pet(“dog”, “Buddy”, age=3)

Question 36

what is local variables and global variables

Answer 36

local variables:
is a variable that is defined inside a function or block of code. It can only be accessed within that function or block and is not visible outside of it.

global variables:
A global variable is a variable that is defined outside any function or block, usually at the top level of the script. It can be accessed by any function or block in the same module (script).

a global variable is read only We cannot modify the value of that variable inside the function directly.

to use global x inside the function for global variable cause functuon automatically takes local variable

Question 37

CSV files read and write and basic syntax

Answer 37

import csv
c=0
with open(“file.csv”) as file:
csvFile=csv.reader(file)
for i in csvFile
if i[7]==”2009”:
c=c+1
print(“number of matches in 2000 are,” c)

i[7]= 7 is the column number

for writing csv

import CSV
c=0
with open(‘file.csv’,’w’) as file:
cw=csv.writer(file)
cs.writerows([‘a,1’][‘b,2’][‘c,3’])

Question 38

implicit, and explicit functions

Answer 38

Explicit Functions: Clearly defined in code by the programmer, specifying the function name, parameters, and behavior. Example:

Implicit Functions: Functions that are invoked automatically or on the fly, often without direct definition or explicit invocation by the programmer. Example:

python
Copy code