Python tutorial

Launch this notebook with:

Open terminal
type cd training/python
type ipython notebook

basics



In [1]:

    
1 + 1









    Out[1]:





2



In [2]:

    
12 * 44









    Out[2]:





528



In [3]:

    
Hello Data Skills!









    



  File "<ipython-input-3-ffc4546b2fc9>", line 1
    Hello Data Skills!
             ^
SyntaxError: invalid syntax



In [4]:

    
'Hello Data Skills!'









    Out[4]:





'Hello Data Skills!'



In [6]:

    
print 'Hello Data Skills!'









    



Hello Data Skills!



In [8]:

    
print "Hello Data Skills!"
print 'Hello Data Skills!'
print """Hello Data Skills!"""









    



Hello Data Skills!
Hello Data Skills!
Hello Data Skills!

types



In [10]:

    
type(1)









    Out[10]:





int



In [11]:

    
type(1 + 1)









    Out[11]:





int



In [21]:

    
type("hello")









    Out[21]:





str



In [13]:

    
1 == 2









    Out[13]:





False



In [14]:

    
1 == 1









    Out[14]:





True



In [15]:

    
type(1 == 1)









    Out[15]:





bool



In [16]:

    
True









    Out[16]:





True



In [17]:

    
False









    Out[17]:





False



In [18]:

    
type(True)









    Out[18]:





bool



In [20]:

    
12 + 12 + "hello"









    



---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-20-756092b166ff> in <module>()
----> 1 12 + 12 + "hello"

TypeError: unsupported operand type(s) for +: 'int' and 'str'



In [22]:

    
str(1)









    Out[22]:





'1'



In [23]:

    
type(str(1))









    Out[23]:





str



In [42]:

    
type(3.14)









    Out[42]:





float



In [71]:

    
3 / 2









    Out[71]:





1



In [72]:

    
3 / 2.0









    Out[72]:





1.5

variables



In [25]:

    
x = 1



In [26]:

    
print x



In [27]:

    
y = x + 2



In [28]:

    
print y



In [29]:

    
z = "hello"



In [30]:

    
z









    Out[30]:





'hello'



In [31]:

    
w = "python"



In [32]:

    
print z + w









    



hellopython



In [33]:

    
print z + " " + w









    



hello python



In [34]:

    
x









    Out[34]:





1



In [35]:

    
x = x + 1



In [36]:

    
print x



In [41]:

    
type(x)









    Out[41]:





int

control statements



In [44]:

    
i = 10
print i % 2



In [45]:

    
i = 9
print i % 2



In [119]:

    
if i % 2 == 0:
    print "even"









    



even



In [48]:

    
if i % 2 == 0:
    print "even"
else:
    print "odd"

odd



In [49]:

    
i = 10



In [51]:

    
# execute "if" the code above with the new value

Excercise: Write a statement which say "it's small" for v < 10 and it says "it's big" for v >= 10



In [87]:

    
v = 1



In [88]:

    
if v < 10:
    print "it's small"
else:
    print "it's big"









    



it's small

Functions



In [52]:

    
def printeven(num):
    if num % 2 == 0:
        print "even"
    else:
        print "false"



In [53]:

    
printeven(10)









    



even



In [54]:

    
printeven(9)









    



false



In [56]:

    
printeven(i)









    



even



In [68]:

    
def printhuf(usd):
    print "$" + str(usd) + " is " + str(272.9 * usd) + " Ft"



In [69]:

    
printhuf(10)









    



$10 is 2729.0 Ft

Exercise: Write a function that converts hufs to dollars and prints them



In [75]:

    
def printusd(huf):
    print str(huf) + " Ft" + " is $" + str(huf / 272.9)



In [76]:

    
printusd(1000)









    



1000 Ft is $3.66434591425



In [96]:

    
def printconvert(amount, currency):
    if currency == "usd":
        printhuf(amount)
    else:
        printusd(amount)



In [93]:

    
printconvert(10, "usd")









    



$10 is 2729.0 Ft

return



In [80]:

    
def tohuf(usd):
    return 272.9 * usd



In [81]:

    
tohuf(10)









    Out[81]:





2729.0



In [153]:

    
x = printhuf(10)









    



$10 is 2729.0 Ft



In [154]:

    
print x









    



None



In [155]:

    
x is None









    Out[155]:





True



In [156]:

    
isnone = x is None



In [157]:

    
print isnone









    



True



In [84]:

    
y = tohuf(10)



In [85]:

    
print y

exercise

create the tousd() function
Create a function that takes an amount and "what" and returns the converted value.



In [99]:

    
# solution
def tousd(huf):
    return huf / 272.9

def convert(amount, currency):
    if currency == "usd":
        return tohuf(amount)
    else:
        return tousd(amount)

print convert(10,"usd")

lists



In [104]:

    
l = [2,4,6]



In [121]:

    
type(l)









    Out[121]:





list



In [101]:

    
print l[0]
print l[2]

2
6



In [102]:

    
print l[3]









    



---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-102-e30cce092d00> in <module>()
----> 1 print l[3]

IndexError: list index out of range



In [105]:

    
l.append(8)



In [106]:

    
print l









    



[2, 4, 6, 8]



In [107]:

    
l[3]









    Out[107]:





8



In [108]:

    
for elem in l:
    print elem



In [112]:

    
range(1,10)









    Out[112]:





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



In [113]:

    
range(1,11)









    Out[113]:





[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]



In [114]:

    
tenelements = range(1,11)



In [115]:

    
for e in tenelements:
    print e



In [118]:

    
for e in tenelements:
    print tohuf(e)

exercise:

create a loop which goes from 1 to 10 but only print the even numbers
transform this loop so it uses an "even" function which returns if a number is even or not (bool)



In [122]:

    
# solution
for e in range(1,11):
    if e % 2 == 0:
        print e



In [123]:

    
def even(num):
    return num % 2 == 0



In [124]:

    
for e in range(1,11):
    if even(e):
        print e

dictionaries



In [127]:

    
u = {
    "username": "lili",
    "password": "1982"
}



In [128]:

    
u["username"]









    Out[128]:





'lili'



In [129]:

    
u["password"]









    Out[129]:





'1982'



In [130]:

    
print u









    



{'username': 'lili', 'password': '1982'}



In [137]:

    
import json



In [142]:

    
with open("passwords.json") as f:
    d = json.load(f)



In [143]:

    
d









    Out[143]:





[{u'password': u'1982', u'username': u'lili'},
 {u'password': u'skateordie', u'username': u'cucu'},
 {u'password': u'imserious', u'username': u'maxwell'}]



In [145]:

    
type(d)









    Out[145]:





list



In [146]:

    
d[2]









    Out[146]:





{u'password': u'imserious', u'username': u'maxwell'}



In [148]:

    
for u in d:
    print u









    



{u'username': u'lili', u'password': u'1982'}
{u'username': u'cucu', u'password': u'skateordie'}
{u'username': u'maxwell', u'password': u'imserious'}



In [149]:

    
for u in d:
    print u["username"]









    



lili
cucu
maxwell

Exercise:

create a function that gets a username as an argument and prints "user found!!" that user is in the json file or not



In [161]:

    
# Solution
def printifinfile(username):
    with open("passwords.json") as f:
        j = json.load(f)
    for record in j:
        if record["username"] == username:
            print "user found!!"



In [162]:

    
printifinfile("lili")









    



user found!!



In [163]:

    
printifinfile("newuser")



In [ ]: