Python 102!, Intermediate Concepts

#Empty List
empty_list = []
empty_list = list()

#creating a list
subjects = ['History', 'Math', 'Physics', 'CS']

#printing the list
print(subjects) 
#Prints all the elements of the list
['History', 'Math', 'Physics', 'CS']

#Prints number of elements in list
print(len(subjects))
#output is 4
4

#Prints the 1st element (History)
print(subjects[0])
#output is history
History

#Prints the last element (CS)
print(subjects[-1])
#output is CS
CS

#Prints the 1st & 2nd element (History)
print(subjects[:2])
#displays output of history and math
['History', 'Math']

#Adds the item at the end of the list
subjects.append('DS')
#printed list with the appended item
print(subjects)
['History', 'Math', 'Physics', 'CS', 'DS']

#Adds the item at index 0
subjects.insert(0,'DBMS')
#printed list with the inserted item at the index 0
print(subjects)
['DBMS', 'History', 'Math', 'Physics', 'CS', 'DS']

num_list = [2,6,4,5,3,1]
num_list.sort()
print(num_list)
[1, 2, 3, 4, 5, 6]
print(min(num_list))
print(max(num_list))
print(sum(num_list))
1
6
21

#Prints each item in new line
for item in subjects:
    print(item)
Art
CS
DBMS
DS
Design
History
Physics

#Print the items along with index numbers starting from 0. this is done by enumerate() function
for index,subject in enumerate(subjects):
    print(index,subject)
0 Art
1 CS
2 DBMS
3 DS
4 Design
5 History
6 Physics

#Empty Tuples
empty_tuple = ()
empty_tuple = tuple()

tup_1 = ('History', 'Math', 'Physics', 'CS')
tup_1[0] = 'Art'
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-25-20f41ff68d0f> in <module>
----> 1 tup_1[0] = 'Art'

TypeError: 'tuple' object does not support item assignment
In [26]:
print(tup_1)
('History', 'Math', 'Physics', 'CS')

cs_courses = {'DS','DBMS','History','Math','Physics'}
#Changes order every time the code executes
print('Math' in cs_courses)
#Checks membership in the set
True

art_courses = {'History','Math','Art','Design'}
#Returns common items in both sets
print(cs_courses.intersection(art_courses))
#display output
{'Math', 'History'}

print(cs_courses.difference(art_courses))

#Returns the items not present in second set
{'DS', 'DBMS', 'Physics'}

print(cs_courses.union(art_courses))

#Prints all the items from both sets dropping the duplicate items in a new set
{'Math', 'History', 'Physics', 'DS', 'Design', 'Art', 'DBMS'}

#Empty sets
empty_set = {} #This will create an empty dictionary instead of empty sets
empty_set = set()

student = {'name':'harsh', 'age':25, 'course':['Math','Physics']}

#prints dictionary with keys & values
print(student) 
{'name': 'harsh', 'age': 25, 'course': ['Math', 'Physics']}

#Prints values of specified key & gives error on the absence of the key
print(student['name'])
harsh

#Prints values of specified key & doesn't gives error on the absence of the key
print(student.get('phone'))
None


#Let's add a phone no to our dictionary
student['phone'] = '999-9999'

student['name'] = 'akshit'
print(student)
#update a key
{'name': 'akshit', 'age': 25, 'course': ['Math', 'Physics'], 'phone': '999-9999'}

#Updating various keys in a single line of code

student.update({'name':'harsh',
               'age': 21,
               'phone': '111-1111'})
print(student)
{'name': 'harsh', 'age': 21, 'course': ['Math', 'Physics'], 'phone': '111-1111'}
In [48]:
#Prints keys from the dictionary

print(student.keys())
dict_keys(['name', 'age', 'course', 'phone'])

#Prints values from the dictionary
print(student.values())
dict_values(['harsh', 21, ['Math', 'Physics'], '111-1111'])

#Iterates and prints only keys from the dictionary
for key in student:
    print(key)
name
age
course
phone
In [ ]:
#Iterates and prints only keys from the dictionary

for key, in student:
    print(key)