Revision

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In this section you will revise all the concepts learnt so far in snippets of code:

try, except, finally block

try: #  try statement encloses statements which could throw an exception
    # input function chained with float function
    deposit_amount = float(input("Enter deposit amount:\t\t")) 
    interest_earned = float(input('Enter total interest earned:\t\t'))
    interest_rate = (interest_earned/deposit_amount) * 100
    # round function rounds the result to 2 decimal places
    print("Rate of interest: \t\t"+ str(round(interest_rate, 2))) 
except:  # catch all exceptions if nothing is specified. 
    print("You entered an invalid integer. Please type a valid value")
finally:
    # typically resources are released in this block
    print("This will be executed no matter what")

for loop

for x in range(0, 3):
    print("Hip hip hurray!  %d" % (x))

output:

Hip hip hurray! 0
Hip hip hurray! 1
Hip hip hurray! 2

while loop

# while loop
x = 1.456
while True:
    print("Integer value of x {:1.0f}".format(x))
    print("Value of x rounded to 2 decimal points {:.2f}".format(round(x, 2)))
    x += 1
    if (x > 3):
        break;

output:

Integer value of x 1
Value of x rounded to 2 decimal points 1.46
Integer value of x 2
Value of x rounded to 2 decimal points 2.46

def function

name = 'My name'
def myfunc(name):
    print("hello there! " +  name) # global name variable is replaced with the local name. 

myfunc("Python")

output:

hello there! Python

not keyword

game_over = False
i = 1;
while not game_over:
    print("playing " + str(i) + " time(s)")
    i += 1
    if (i > 2):
        break

output:

playing 1 time(s)
playing 2 time(s)

Sending list to a function

# sending list to function
topics = ["numpy",'pandas',"seaborn"]
def displayTopics(topics):
    for topic in topics:
        print(topic)

displayTopics(topics)

output:

numpy
pandas
seaborn

List of lists - 2d

topics = [
         ['numpy', 1],
         ['pandas',2],
         ['seaborn',3]
         ]

print(topics)
print(topics[1][0])

output:

[['numpy', 1], ['pandas', 2], ['seaborn', 3]]
pandas

Tuples

# Tuples are immutable
t_tuples = ('numpy', "pandas", "seaborn")
print(t_tuples[0])
a,b,c = t_tuples  #tuples can be unpacked into multiple assignment statements
print(b)
# tuples are more efficient than lists so for readonly structures use tuples

output:

numpy
pandas

String search

message = "Congratulations!  you are all set to move on to numpy and pandas!"
print('you' in message)
print('congratulations' in message) # case sensitive
for char in "study":
    print(char)
print(message.startswith("Congratulations"))

output:

True
False
s
t
u
d
y
True

String manipulations

numbers = "12345"
print(numbers.isdigit()) # Other functions; islower(), isupper(), isalpha()

message = "this is really easy!"
print(message.title())

phoneNumber = "123 234 3489    "
print(phoneNumber.strip() + ".")
print(phoneNumber.replace(" ", "-"))  
print("(" + phoneNumber[:3] + ")"+ phoneNumber[4:7] + "-"+ phoneNumber[8:13])
print(phoneNumber.split(" "))

# Justifies to the given length by adding spaces to fill the gap
print("book".ljust(14), "$9.99".rjust(10))  

print(message.upper())

output:

True
This Is Really Easy!
123 234 3489.
123-234-3489----
(123)234-3489
['123', '234', '3489', '', '', '', '']
book                 $9.99
THIS IS REALLY EASY!

datetime module

from datetime import date
from datetime import datetime
print(date.today())
print(datetime.now())
peace_day = datetime(1981, 9, 21, 17, 30)
print(peace_day)
print(peace_day.strftime("%Y/%m/%d"))

output:

[the date this program is run]
[the date and time this program is run]
1981-09-21 17:30:00
1981/09/21>

Dictionaries

are unordered collection. Keys are indexed, Key can be any immutable type and value can be any type including mutable types

countries = {'CA': "Canada",
            "US":"United States",
            "MX": "Mexico",
            3:10
            }
print (countries)
print(countries['CA'])
code = 'US'
if code in countries:
    print(countries[code])

print(countries.get("mx"))  # Case sensitive
print(countries.get("MX"))

countries['IN'] = "India"
print(countries['IN'])
countries['IN'] = 'Bharath'
print(countries['IN']) 
del countries['MX']
print(countries)
countries.pop("IN")  # You can use del, pop methods to remove an item from dictionary. clear() removes all items
print(countries)
print(countries.keys())
print(countries.values())
for name in countries.values():
    print (name)

for code,name in countries.items():  # Unpack tuples
    print(code , name)

output:

{'CA': 'Canada', 'US': 'United States', 'MX': 'Mexico', 3: 10}
Canada
United States
None
Mexico
India
Bharath
{'CA': 'Canada', 'US': 'United States', 3: 10, 'IN': 'Bharath'}
{'CA': 'Canada', 'US': 'United States', 3: 10}
dict_keys(['CA', 'US', 3])
dict_values(['Canada', 'United States', 10])
Canada
United States
10
CA Canada
US United States
3 10

More dictionary manipulations

# Convert dictionary to list
codes = list(countries.keys())
print(type(codes))
del codes[2] # remove the integer so sort can work

codes.sort() 
print(codes)

output:

<class 'list'>
['CA', 'US']