Lists

Basic Lists



In [169]:

    
my_cars = ['BMW 320', 'Benz C class', 'Porshe', 'Maruthi 800']



In [170]:

    
len(my_cars)









    Out[170]:





4



In [171]:

    
print my_cars[0]



In [172]:

    
print my_cars[1]









    



Benz C class



In [173]:

    
print my_cars[10000]









    



---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-173-32137b93c120> in <module>()
----> 1 print my_cars[10000]

IndexError: list index out of range

Does not clone by default



In [174]:

    
my_favourites = my_cars



In [175]:

    
type(my_cars)









    Out[175]:





list



In [176]:

    
my_favourites.append("Tesla Model S")



In [177]:

    
my_cars









    Out[177]:





['BMW 320', 'Benz C class', 'Porshe', 'Maruthi 800', 'Tesla Model S']

`+` operator works just fine



In [178]:

    
awesome_people = ["T.R", "Vijaykanth"]



In [179]:

    
awesome_cars = ["BMW", "Merc"]



In [180]:

    
awesome_things = awesome_people + awesome_cars



In [181]:

    
awesome_things









    Out[181]:





['T.R', 'Vijaykanth', 'BMW', 'Merc']



In [182]:

    
awesome_cars + awesome_people









    Out[182]:





['BMW', 'Merc', 'T.R', 'Vijaykanth']

Traversing a list



In [183]:

    
for car in my_cars:
    print car, "is my car!"









    



BMW 320 is my car!
Benz C class is my car!
Porshe is my car!
Maruthi 800 is my car!
Tesla Model S is my car!

Note: Do NOT add or remove an element during iteration



In [184]:

    
def cube(x):
    return x*x*x

nums = [1,2,3,4,5,6]
cubed_nums = []
for num in nums:
    cubed_nums.append(cube(num))
    
print cubed_nums









    



[1, 8, 27, 64, 125, 216]

Checking if list contains an element



In [185]:

    
"BMW 320" in my_cars









    Out[185]:





True



In [187]:

    
if "BMW 320" in my_cars:
    print "i am a rich man"









    



i am a rich man



In [186]:

    
"Maruthi Zen" in my_cars









    Out[186]:





False



In [188]:

    
a_string = "Hello World"
for every_character in a_string:
    print "[" + every_character + "]"









    



[H]
[e]
[l]
[l]
[o]
[ ]
[W]
[o]
[r]
[l]
[d]



In [189]:

    
long_string = "The quick brown fox jumps over the lazy dog"



In [190]:

    
long_string.split(" ")









    Out[190]:





['The', 'quick', 'brown', 'fox', 'jumps', 'over', 'the', 'lazy', 'dog']



In [191]:

    
long_string.title()









    Out[191]:





'The Quick Brown Fox Jumps Over The Lazy Dog'



In [194]:

    
cap_words = []
for word in long_string.split():
    cap_words.append(word.capitalize())
    
cap_words









    Out[194]:





['The', 'Quick', 'Brown', 'Fox', 'Jumps', 'Over', 'The', 'Lazy', 'Dog']



In [196]:

    
"_".join(cap_words)









    Out[196]:





'The_Quick_Brown_Fox_Jumps_Over_The_Lazy_Dog'



In [197]:

    
" ".join([1,2,3])









    



---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-197-a74a1b54c8da> in <module>()
----> 1 " ".join([1,2,3])

TypeError: sequence item 0: expected string, int found

Ranges



In [198]:

    
range(10)









    Out[198]:





[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]



In [200]:

    
for i in range(10):
    print i



In [201]:

    
range(5, 10)









    Out[201]:





[5, 6, 7, 8, 9]



In [202]:

    
range(5, 10, 2)









    Out[202]:





[5, 7, 9]



In [203]:

    
for num in range(10):
    print cube(num)

Using a while loop



In [204]:

    
i=0
while i < len(my_cars):
    print my_cars[i]
    i += 2









    



BMW 320
Porshe
Tesla Model S



In [ ]:

    
my_cars

Methods on Lists

Append



In [205]:

    
my_cars = []



In [206]:

    
my_cars









    Out[206]:





[]



In [207]:

    
my_cars.append("BMW 320")



In [208]:

    
my_cars.append("Tesla Model S")



In [209]:

    
my_cars









    Out[209]:





['BMW 320', 'Tesla Model S']

Note: Doesn't return a new list, modifies the original

Insert



In [210]:

    
my_cars









    Out[210]:





['BMW 320', 'Tesla Model S']



In [211]:

    
my_cars.insert(0, "Merc C Class")



In [212]:

    
my_cars









    Out[212]:





['Merc C Class', 'BMW 320', 'Tesla Model S']

Extend



In [213]:

    
his_cars = ["Maruthi 800"]



In [214]:

    
my_cars









    Out[214]:





['Merc C Class', 'BMW 320', 'Tesla Model S']



In [215]:

    
my_cars.extend(his_cars)



In [216]:

    
my_cars









    Out[216]:





['Merc C Class', 'BMW 320', 'Tesla Model S', 'Maruthi 800']



In [217]:

    
a = [1,2]



In [218]:

    
b = [3,4]



In [219]:

    
a.append(b)



In [220]:

    
a









    Out[220]:





[1, 2, [3, 4]]

Index



In [221]:

    
my_cars.index("BMW 320")









    Out[221]:





1



In [222]:

    
my_cars[1]









    Out[222]:





'BMW 320'



In [223]:

    
my_cars.index("Porshe")









    



---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-223-9418d51d0ea0> in <module>()
----> 1 my_cars.index("Porshe")

ValueError: 'Porshe' is not in list

Remove



In [224]:

    
my_cars.remove("BMW 320")



In [225]:

    
my_cars









    Out[225]:





['Merc C Class', 'Tesla Model S', 'Maruthi 800']



In [226]:

    
my_cars.remove("BMW 320")









    



---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-226-f626228cdf13> in <module>()
----> 1 my_cars.remove("BMW 320")

ValueError: list.remove(x): x not in list

Sort



In [227]:

    
my_cars









    Out[227]:





['Merc C Class', 'Tesla Model S', 'Maruthi 800']



In [228]:

    
my_cars.sort()



In [229]:

    
my_cars









    Out[229]:





['Maruthi 800', 'Merc C Class', 'Tesla Model S']

Reverse



In [230]:

    
my_cars









    Out[230]:





['Maruthi 800', 'Merc C Class', 'Tesla Model S']



In [231]:

    
my_cars.reverse()



In [232]:

    
my_cars









    Out[232]:





['Tesla Model S', 'Merc C Class', 'Maruthi 800']

Pop



In [233]:

    
my_cars









    Out[233]:





['Tesla Model S', 'Merc C Class', 'Maruthi 800']



In [234]:

    
my_cars.pop()









    Out[234]:





'Maruthi 800'



In [235]:

    
my_cars









    Out[235]:





['Tesla Model S', 'Merc C Class']



In [236]:

    
my_cars.pop(0)









    Out[236]:





'Tesla Model S'



In [237]:

    
my_cars









    Out[237]:





['Merc C Class']

Note: All of the above methods work IN-PLACE, meaning that they don't return any result

Slicing in Lists



In [238]:

    
till_100 = range(100)



In [239]:

    
till_100









    Out[239]:





[0,
 1,
 2,
 3,
 4,
 5,
 6,
 7,
 8,
 9,
 10,
 11,
 12,
 13,
 14,
 15,
 16,
 17,
 18,
 19,
 20,
 21,
 22,
 23,
 24,
 25,
 26,
 27,
 28,
 29,
 30,
 31,
 32,
 33,
 34,
 35,
 36,
 37,
 38,
 39,
 40,
 41,
 42,
 43,
 44,
 45,
 46,
 47,
 48,
 49,
 50,
 51,
 52,
 53,
 54,
 55,
 56,
 57,
 58,
 59,
 60,
 61,
 62,
 63,
 64,
 65,
 66,
 67,
 68,
 69,
 70,
 71,
 72,
 73,
 74,
 75,
 76,
 77,
 78,
 79,
 80,
 81,
 82,
 83,
 84,
 85,
 86,
 87,
 88,
 89,
 90,
 91,
 92,
 93,
 94,
 95,
 96,
 97,
 98,
 99]



In [240]:

    
till_100[:5]









    Out[240]:





[0, 1, 2, 3, 4]



In [241]:

    
till_100[-5:]









    Out[241]:





[95, 96, 97, 98, 99]



In [242]:

    
till_100[0] = "Booga"



In [250]:

    
for i in till_100[:5]:
    print type(i) is int









    



False
True
True
True
True



In [247]:

    
help(instance of)









    



  File "<ipython-input-247-4697f9012d87>", line 1
    help(instance of)
                   ^
SyntaxError: invalid syntax



In [252]:

    
isinstance("hello", str)









    Out[252]:





True



In [245]:

    
till_100[:5]









    Out[245]:





['Booga', 1, 2, 3, 4]

Exercises

A and B of basic/list1.py