Lists



In [1]:

    
a = 5
name = "Shantnu"
print(a)
print(name)









    



5
Shantnu



In [2]:

    
names = ["Shantnu", "John", "Sally"]
print(names)









    



['Shantnu', 'John', 'Sally']



In [3]:

    
for name in names:
    print("Hello ", name)









    



Hello  Shantnu
Hello  John
Hello  Sally



In [14]:

    
names.append("Mr Smith")
print(names)









    



['Shantnu', 'John', 'Sally', 'Mr Smith']



In [5]:

    
# Ipython only! be careful
names









    Out[5]:





['Shantnu', 'John', 'Sally', 'Mr Smith']



In [7]:

    
# Start from 0
print(names[0])
print(names[2])









    



Shantnu
Sally



In [9]:

    
# Weird!

print(names[-1])

# prints last value

print(names[-2])









    



Mr Smith
Sally



In [11]:

    
# learn to google! Remove from list
names.append("Wrong name! Please remove me")
print(names)









    



['Shantnu', 'John', 'Sally', 'Mr Smith', 'Wrong name! Please remove me', 'Wrong name! Please remove me']
['Shantnu', 'John', 'Sally', 'Mr Smith', 'Wrong name! Please remove me']



In [13]:

    
del names[-1]
print(names)









    



['Shantnu', 'John', 'Sally']



In [15]:

    
names









    Out[15]:





['Shantnu', 'John', 'Sally', 'Mr Smith']



In [17]:

    
# Array slicing
# Add another few names. Make it 10
names.append("K")
names.append("l")
names.append("m")
names.append("n")
names









    Out[17]:





['Shantnu', 'John', 'Sally', 'Mr Smith', 'K', 'l', 'm', 'n']



In [18]:

    
# prnt 1st five names
names[:5]









    Out[18]:





['Shantnu', 'John', 'Sally', 'Mr Smith', 'K']



In [19]:

    
names[5:]









    Out[19]:





['l', 'm', 'n']



In [20]:

    
# And this is where it gets interetsing

names[2:6]









    Out[20]:





['Sally', 'Mr Smith', 'K', 'l']



In [26]:

    
# You can even do
# removes 1st and last valyues!
names[1:-1]









    Out[26]:





['John', 'Sally', 'Mr Smith', 'K', 'l', 'm']



In [27]:

    
# Go from 2 to 6 in steps of 2
names[2:6:2]









    Out[27]:





['Sally', 'K']



In [37]:

    
# If loop

for name in names:
    if (name == "Sally"):
        print("Found Sally!")
    elif (name == "l"):
        print("Mr T found")
    else:
        print("Unknown name")









    



Unknown name
Unknown name
Found Sally!
Unknown name
Unknown name
Mr T found
Unknown name
Unknown name

Dictionary



In [28]:

    
age_dict = {"Bob":21, "Sally":33, "L":2}
age_dict









    Out[28]:





{'Bob': 21, 'L': 2, 'Sally': 33}



In [29]:

    
age_dict["Bob"]









    Out[29]:





21



In [30]:

    
age_dict["Shantnu"] = 16
age_dict









    Out[30]:





{'Bob': 21, 'L': 2, 'Sally': 33, 'Shantnu': 16}

List comprehension



In [34]:

    
# We have a list. Divide each value by 5

numbers = [5,10,15,20,25]
numbers2 = []

for n in numbers:
    numbers2.append(n / 5)
    
print(numbers)    
print(numbers2)









    



[5, 10, 15, 20, 25]
[1.0, 2.0, 3.0, 4.0, 5.0]



In [35]:

    
numbers3 = [ n / 5 for n in numbers]
print(numbers3)









    



[1.0, 2.0, 3.0, 4.0, 5.0]



In [36]:

    
import numpy as np

numbers_np = np.array(numbers)
numbers_np = numbers_np / 5

print(numbers_np)









    



[ 1.  2.  3.  4.  5.]

Strings



In [39]:

    
# Strings are like lists!

name = "Shantnu"
for n in name:
    print(n)









    



S
h
a
n
t
n
u



In [40]:

    
sirname = "Tiwari"
print(name + sirname)









    



ShantnuTiwari

File I/o

Save the following into a file called names.txt

Shantnu, John, Sally, Mr Smith



In [42]:

    
with open("names.txt", "r") as f:
    names_file = f.read()
print(names_file)









    



Shantnu, John, Sally, Mr Smith



In [44]:

    
names_file_separate = names_file.split(",")
names_file_separate









    Out[44]:





['Shantnu', ' John', ' Sally', ' Mr Smith']



In [54]:

    
names_file_separate = [name.replace(" ", "") for name in names_file_separate]
names_file_separate









    Out[54]:





['Shantnu', 'John', 'Sally', 'MrSmith']

Functions



In [55]:

    
def hello(name):
    print("Hello ", name)
    
hello("Shantnu")









    



Hello  Shantnu



In [56]:

    
def hello2(name):
    return "Hello " + name
    
print(hello2("Shantnu")  )









    



Hello Shantnu



In [57]:

    
def hello_age(name, age):
    name_hello = "Hello " + name
    age = age  + 10
    return name_hello, age

name_hello, age = hello_age("Shan", 16)
print("Hello {} in 10 years you will be {} years old! Shocking".format(name_hello, age ))









    



Hello Hello Shan in 10 years you will be 26 years old! Shocking



In [ ]: