Python - List Questions Flashcards
a = [1,2,3,4,5,6,7,8]
a[1:4]
a = [1,2,3,4,5,6,7,8]
a[1:4]
returns [2,3,4]
indexes at 0 and does NOT include the last index
a = [1,2,3,4,5,6,7,8]
a[1:4:2]
a = [1,2,3,4,5,6,7,8]
a[1:4:2]
returns [2, 4]
slices along increments of 2 starting at your first index listed
a = [1,2,3,4,5,6,7,8]
a[ : : -1]
a = [1,2,3,4,5,6,7,8]
a[ : : -1]
returns [8, 7, 6, 5, 4, 3, 2, 1]
slices the list in reverse
a = [1, 2, 3, 4, 5]
sliceObj = slice(1, 3)
a[sliceObj]
a = [1, 2, 3, 4, 5]
sliceObj = slice(1, 3)
a[sliceObj]
return [2, 3]
lst = [x ** 2 for x in range (1, 11) if x % 2 == 1]
lst = [x ** 2 for x in range (1, 11) if x % 2 == 1]
x ** 2 is output expression,
range (1, 11) is input sequence,
x is variable and
if x % 2 == 1 is predicate part.
odd_square = [x ** 2 for x in range(1, 11) if x % 2 == 1]
print odd_square
odd_square = [x ** 2 for x in range(1, 11) if x % 2 == 1]
print odd_square
list contains square of all odd numbers from range 1 to 10
power_of_2 = [2 ** x for x in range(1, 9)]
print power_of_2
power_of_2 = [2 ** x for x in range(1, 9)]
print power_of_2
list contains power of 2 from 1 to 8
noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)]
primes = [x for x in range(2, 50) if x not in noprimes]
print primes
list contains prime and non-prime in range 1 to 50
noprimes = [j for i in range(2, 8) for j in range(i*2, 50, i)]
primes = [x for x in range(2, 50) if x not in noprimes]
print primes
print [x.lower() for x in [“A”, “B”, “C”]]
print [x.lower() for x in [“A”, “B”, “C”]]
list for lowering the characters
string = “my phone number is : 11122 !!”
print(“\nExtracted digits”)
numbers = [x for x in string if x.isdigit()]
print numbers
string = “my phone number is : 11122 !!”
print(“\nExtracted digits”)
numbers = [x for x in string if x.isdigit()]
print numbers
list which extracts number
a = 5 table = [[a, b, a * b] for b in range(1, 11)]
print(“\nMultiplication Table”)
for i in table:
print i
a = 5 table = [[a, b, a * b] for b in range(1, 11)]
print(“\nMultiplication Table”)
for i in table:
print i
A list of list for multiplication table
lst = filter(lambda x : x % 2 == 1, range(1, 20))
print lst
# filtering odd numbers lst = filter(lambda x : x % 2 == 1, range(1, 20)) print lst
We can use FILTER function to filter a list based on some condition provided as a ___________ as first argument and list as second argument.
We can use FILTER function to filter a list based on some condition provided as a ___________ as first argument and list as second argument.
lambda expression
lst = filter(lambda x : x % 5 == 0,
[x ** 2 for x in range(1, 11) if x % 2 == 1])
print lst
# filtering odd square which are divisble by 5
lst = filter(lambda x : x % 5 == 0,
[x ** 2 for x in range(1, 11) if x % 2 == 1])
print lstlst = filter((lambda x: x < 0), range(-5,5))
print lst
# filtering negative numbers lst = filter((lambda x: x < 0), range(-5,5)) print lst
print reduce(lambda a,b: a if (a > b) else b, [7, 12, 45, 100, 15])
# implementing max() function, using print reduce(lambda a,b: a if (a > b) else b, [7, 12, 45, 100, 15])
“in” operator
“in” operator: This operator is used to check if an element is present in the list or not. Returns true if element is present in list else returns false.
ex) lis = [1, 4, 3, 2, 5]
if 4 in lis:
print ….
“not in” operator
“not in” operator : This operator is used to check if an element is not present in the list or not. Returns true if element is not present in list else returns false.
ex) lis = [1, 4, 3, 2, 5]
if 4 not in lis:
print ….
len()
len() : This function returns the length of list.
min()
min() :- This function returns the minimum element of list.
max()
max() :- This function returns the maximum element of list.
+ operator
“+” operator :- This operator is used to concatenate two lists into a single list.
- operator
“*” operator :- This operator is used to multiply the list “n” times and return the single list.
index(ele, beg, end)
index(ele, beg, end) :- This function returns the index of first occurrence of element after beg and before end.
# using index() to print first occurrence of 3
# prints 5
print ("The first occurrence of 3 after 3rd position is : ", end="")
print (lis.index(3, 3, 6))
count()
count() :- This function counts the number of occurrences of elements in list.
# using count() to count number of occurrence of 3
print ("The number of occurrences of 3 is : ", end="")
print (lis.count(3))
del[a : b]
del[a : b] :- This method deletes all the elements in range starting from index ‘a’ till ‘b’ mentioned in arguments.
pop()
pop(): This method deletes the element at the position mentioned in its arguments.
insert(a, x)
insert(a, x) :- This function inserts an element at the position mentioned in its arguments. It takes 2 arguments, position and element to be added at respective position.
remove()
remove() :- This function is used to delete the first occurrence of number mentioned in its arguments.
sort()
sort() :- This function sorts the list in increasing order.
reverse()
reverse() :- This function reverses the elements of list.
extend(b)
extend(b) :- This function is used to extend the list with the elements present in another list. This function takes another list as its argument.
clear()
clear() :- This function is used to erase all the elements of list. After this operation, list becomes empty.
