Assigning variables¶

In [2]:

print('Hello World')

Hello World

In [5]:

pi = 3.14159265359    # decimal
name = 'Philipp'      # text
age = 31              # integer
sky_is_blue = True    # boolean

In [4]:

print(pi)

3.14159265359

Packing multiple assignments on one line¶

In [6]:

x, y = 10, 5
print(x)

In [7]:

print(y)

Re-assigning (Updating the variable)¶

In [8]:

pi = 'Philipp'
print(pi)

Philipp

In [9]:

x, y = y, x

In [10]:

Out[10]:

Using non-defined variables will raise a NameError¶

In [11]:

print(non_existent_variable)

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-11-5ebcdcc221cf> in <module>()
----> 1 print(non_existent_variable)

NameError: name 'non_existent_variable' is not defined

Tips - other ways to define value¶

In [13]:

ten_millions = 10_000_000
ten_millions

Out[13]:

10000000

In [14]:

small = .25
small

Out[14]:

0.25

In [15]:

sci_thousand = 10e2
sci_thousand

Out[15]:

1000.0

Naming the variable¶

No keywords and operator symbols (class, def, for, ..., +, -, @, etc)
No whitespace
Cannot start with number

In [1]:

counter = 0
pricey_car = 'Mercedes'
income = 120_000

In [2]:

class = 'Mercedes'

  File "<ipython-input-2-2daee69c2fcb>", line 1
    class = 'Mercedes'
          ^
SyntaxError: invalid syntax

In [3]:

pricey@@car

  File "<ipython-input-3-ffd8cc768d68>", line 1
    pricey@@car
           ^
SyntaxError: invalid syntax

In [4]:

1y_income = 120_000

  File "<ipython-input-4-2b923f9c6b91>", line 1
    1y_income = 120_000
            ^
SyntaxError: invalid syntax

Data types¶

In [17]:

pi = 3.14159265359    # reassing it back
type(pi)

Out[17]:

float

In [18]:

type(name)

Out[18]:

str

In [20]:

type(age)

Out[20]:

int

In [19]:

type(sky_is_blue)

Out[19]:

bool

Floats and Integers¶

In [21]:

A = 6
B = 5

In [22]:

A + B

Out[22]:

In [23]:

A - B

Out[23]:

In [24]:

A / B

Out[24]:

1.2

In [25]:

A * B

Out[25]:

Exponent

In [26]:

2**3

Out[26]:

In [27]:

3**2

Out[27]:

Integer division

In [28]:

10 / 2

Out[28]:

5.0

In [87]:

9 // 4  # way faster

Out[87]:

In [88]:

10.0 // 4
2.0

Out[88]:

2.0

Reminer

In [89]:

10 % 3

Out[89]:

Self-assignment¶

In [79]:

count = 0

In [80]:

count +=1
count

Out[80]:

In [81]:

count -=1
count

Out[81]:

In [82]:

count +=1
count *=2
count

Out[82]:

In [83]:

count **= 2
count

Out[83]:

In [84]:

count /=2
count

Out[84]:

2.0

In [85]:

count //= 2
count

Out[85]:

1.0

In [86]:

10.0 // 4

Out[86]:

2.0

Order of operations¶

In [90]:

(2 + 10) / 2

Out[90]:

6.0

In [91]:

10 / (1 + 1)

Out[91]:

5.0

Strings¶

In [93]:

text1 = 'This is a so-called “speakeasy”'

In [94]:

text2 = "This is Sam’s Tavern"

In [95]:

text3 = ''' This is Sam’s Tavern.
"Welcome everyone!" - is written on the door.
'''

In [96]:

print('Hello\nWorld!')

Hello
World!

Operators¶

In [97]:

'Hello ' + 'World'

Out[97]:

'Hello World'

In [98]:

'Hello' * 3

Out[98]:

'HelloHelloHello'

Methods¶

In [99]:

'Hello World'.upper()

Out[99]:

'HELLO WORLD'

In [100]:

'Hello World'.lower()

Out[100]:

'hello world'

In [101]:

'hello world'.title()

Out[101]:

'Hello World'

In [102]:

'Hello world'.replace('world', 'planet')

Out[102]:

'Hello planet'

Formatting¶

In [106]:

'hello'.rjust(10, ' ')

Out[106]:

'     hello'

In [107]:

'hello'.ljust(10, ' ')

Out[107]:

'hello     '

In [108]:

'999'.zfill(10)

Out[108]:

'0000000999'

Format method

In [110]:

'Hello {} world and our blue {}'.format('beautiful','planet')

Out[110]:

'Hello beautiful world and our blue planet'

In [111]:

'{0} {2} {1} and our {2} {3}!'.format('Hello','World','Beautiful', 'Planet')

Out[111]:

'Hello Beautiful World and our Beautiful Planet!'

In [114]:

'Hello {adj} world!'.format(adj='beautiful')

Out[114]:

'Hello beautiful world!'

F-strings

In [116]:

adj = 'beautiful'
f'Hello {adj} world!'

Out[116]:

'Hello beautiful world!'

In [118]:

name = 'pHILIPP'
f'Hello mr {name.title()}'

Out[118]:

'Hello mr Philipp'

Legacy formatting (do not use)

In [119]:

name = 'David'
print('Hello mr. %s' % name)

Hello mr. David

Formatting mini-language

In [121]:

pct = .345
value = 45500
f'Price grew by {pct:.1%} or {value:,}'

Out[121]:

'Price grew by 34.5% or 45,500'

Formatting mini-language link

String as iterable¶

In [47]:

"Hello World"[0]

Out[47]:

'H'

In [48]:

"Hello World"[0:5]

Out[48]:

'Hello'

In [50]:

"World" in "Hello World!"

Out[50]:

True

In [51]:

"Planet" in "Hello World!"

Out[51]:

False

Boolean¶

In [122]:

'World' == 'World'

Out[122]:

True

In [123]:

pi == pi

Out[123]:

True

In [124]:

"World" in "Hello World!"

Out[124]:

True

In [125]:

pi != pi

Out[125]:

False

Logical operators¶

In [130]:

not (5 > 4)

Out[130]:

False

In [131]:

(5 > 4) | (6 < 5)

Out[131]:

True

In [132]:

(5 > 4) & (6 < 5)

Out[132]:

False

In [133]:

(5 > 4) ^ (5 < 6)

Out[133]:

False

Conversion¶

In [66]:

float("2.5")

Out[66]:

2.5

In [67]:

int("45")

Out[67]:

In [68]:

int(4.521)

Out[68]:

In [69]:

float(5)

Out[69]:

5.0

In [70]:

int(True)

Out[70]:

In [71]:

float(False)

Out[71]:

0.0

In [134]:

str(True)

Out[134]:

'True'

In [72]:

bool(0)

Out[72]:

False

In [73]:

bool('Hello')

Out[73]:

True

In [74]:

bool(115.5)

Out[74]:

True

Can't convert

In [135]:

int("2.5")

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-135-b44af7edf778> in <module>()
----> 1 int("2.5")

ValueError: invalid literal for int() with base 10: '2.5'

In [136]:

int("Hello")

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-136-b6a8c1f9fea6> in <module>()
----> 1 int("Hello")

ValueError: invalid literal for int() with base 10: 'Hello'

Practice¶

In [137]:

people = 2
days = 7

In [138]:

plane_ticket_pp = 180
hotel_price_day = 85  
meal_pp = 13

In [139]:

total_budget = 1000

Calculate main costs¶

In [140]:

total_travel = people * plane_ticket_pp
total_hotel = hotel_price_day * days
total_meal = 3 * days * people
total = total_travel + total_hotel + total_meal

Check if they exceeded our budget¶

In [141]:

exceeded = total > total_budget
exceeded

Out[141]:

False

Generate report¶

In [143]:

report = f'Estimated travel price is ${total:,} and represents {(total / total_budget):%} of existing travel budget.\nEstimate exceeds travel budget: {exceeded}.'
print(report)

Estimated travel price is $997 and represents 99.700000% of existing travel budget.
Estimate exceeds travel budget: False.

In [ ]: