Download the lecture slides for our python notebooks:

python notebooks link: https://github.com/rreggiar/ucsc_scbc_2022/raw/master/slides/02_intro_python/02_intro_python.ipynb

mkdir python_notebooks
cd python_notebooks
wget https://github.com/rreggiar/ucsc_scbc_2022/raw/master/slides/02_intro_python/02_intro_python.ipynb

Double click on student_python_L01.ipynb on your jupyterhub launch page

A jupyter notebook should have popped up- let me know if it hasn't

This is an example of a code block in Jupyter notebooks

print('Hi, this is a code block')

To run the code block, click the cell, and then click the "Run" icon on the toolbar above

print('Hi, this is a run code block')

Hi, this is a run code block

Welcome to Python!

Python is a coding language, like bash

What happens in python stays in python- variables won't carry to bash

Python syntax is different from bash syntax

The concepts of coding are still the same

Comments

# This is a comment

# Code can be hard to read, and yet you 
# often have to edit and maintain code over time.

# Comments let you keep notes in your code.

# Rule of thumb: Good code is often about 50% code and 50% comments

# It is amazing to read code you wrote last year - you
# likely won't remember how it works without comments!

# It is a good idea to try to keep your comments to less than 80 or so characters by spreading them across multiple lines. 

Hello, world

Okay, let's run our first program...

# Hello world program - this is a comment 

Hello, world!

# (it's just to make the code readable)

# Go ahead and run this by hitting the run (play) button
print("Hello, world!") 

Practice 1

What command is print() similar to in bash?

Try this practice problem:

print the words "I love python" in the code block below

# replace the text here  with your answer

Computers store data as variables

Example:

• what is the variable here?
• what value are we assigning to the variable?
• what is the value of b?

a = 1
b = a
# how could you check the value of b? 

print(b)

1

Variables can be different datatypes

Different datatypes have specific operations

You can sum two numbers to get a new number

What happens if you sum two words?

# add "Roman loves " and "bioinformatics"
s = "Roman loves " + "bioinformatics"

print(s)

The datatypes you'll usually encounter are:

• integer = int
  • an integer (1)
• floating point = float
  • a floating point number (3.14)
• string = str
  • a list of characters ("bioinformatics")
• boolean = bool
  • True or False
• list = list
  • a list of variables
• dictionary = dict
  • a key value pair (don't worry about this now)

type() lets you check the datatype of a variable

This is an example of a function in python

type() is built into python

what are the datatypes of the variables below?

Using type()

type(1)

Okay, so what's the type of a decimal?

type(3.142)

type(3.142)

And the type of 1.0?

type(1.0)

type(1.0)

What about text?

type("hello")

type("hello")

# Find out the type of x
x = [ 1, 2, 3 ]

# your code here

What went wrong here?

# I want the text to say 
t = "my favorite number is " + 8
print(t)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [32], in <cell line: 2>()
      1 # I want the text to say 
----> 2 t = "my favorite number is " + 8
      3 print(t)

TypeError: can only concatenate str (not "int") to str

What is the type of "my favorite number is "?

What is the type of 8?

Can we change the type of 8?

Yes! This is called "Type Casting"

#turn 8 into a string
t = "my favorite number is " + str(8)
print(t)

my favorite number is 8

You can type cast using the same definitions above:

• integer = int
  • an integer (1)
• floating point = float
  • a floating point number (3.14)
• string = str
  • a list of characters ("bioinformatics")

type(str(10.00))

str

type(int(9.24))

int

What's the issue here?

type(float("a"))

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
Input In [45], in <cell line: 1>()
----> 1 type(float("a"))

ValueError: could not convert string to float: 'a'

Lists are a datatype used to store other variables

You can define lists using square brackets []

List elements are separated by commas

[element_one, element_two, element_three]

You can assign a list to a variable

my_list = [element_one, element_two, element_three]

Here's a list named "BSCC" with the first names of your teaching staff

BSCC_teachers = ['Roman','Vikas','Sarah','Daniel']
# question: why do we have to put the names in quotes? 

You can access elements in list using an "index"

BSCC_teachers = ['Roman','Vikas','Sarah','Daniel']

Sarah's name is the second position in the list

• The second element??
• Python is "0 indexed", so it starts counting at 0
• Roman:0 Vikas:1 Sarah:2 Daniel:3

You can access the list element using another square bracket [2]

BSCC_teachers[2]

'Sarah'

Given the alphabet below, print the 18th letter

alphabet = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z']

# your code goes here

Debugging practice:

What happened here?

print(alphabet[35])

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Input In [14], in <cell line: 1>()
----> 1 print(alphabet[35])

IndexError: list index out of range

You can add to a list using the .append() function

dog_names = ['Chewbacca', 'Bark_Twain', 'Salvador Dogi']
print(dog_names)
dog_names.append('mary_puppins')
print(dog_names)

['Chewbacca', 'Bark_Twain', 'Salvador Dogi']
['Chewbacca', 'Bark_Twain', 'Salvador Dogi', 'mary_puppins']

Notice how we didn't have to save dog_names when using .append()

.append() performs the action in place

Append your name to the BSCC_teachers list

# your code here

Operators are used to perform operations on variables

math operators perform math operations on variables

• + adds variables
• - subtracts variables
• * multiplies variables
• / divides variables
• ** raises the variable on the right to the power of the variable on the left
  • 3^2 is 9
  • 2^3 is 8
• () parantheses separate the order of operations
  • (2 + 8) / 2 = 5
  • 2 + 8 / 2 = 6

Challenge: If Diameter is the DIAMETER of the circle, find the area of the circle and store it in the variable area

Diameter = 31
Pi = 3.14

# your code here

Operators for comparing variables in python

comparison operators in python will return Boolean (True or False) values

• > ,< greater than and less than
• >= ,<= greater than or equal to and less than or equal to
• == equal to (remember, = assigns a variable)
• != not equal to

check if the area of the circle created in the last slide is greater than 10

check if the area of the circle created in the last slide is less than or equal to 50

hint: you'll have to wrap these in a print statement as well

# You stored the area of the circle in the variable area
# your code here

Challenge:

Raise the second element of list_one to the power of the fifth element of list_two and store it in the variable A

Raise the first element of list_two to the power of the third element of list_one and store it in the variable B

Create a list, C, containing A and B

Using operators, is A greater than B?

Check if your values for A and B match the answers A_answer and B_answer

list_one = [2014,242,223,583,6712]
list_two = [4526,6565,2324,134342,3845,6542]
# your code here

A = list_one[1] ** list_two[4]
B = list_two[0] ** list_one[2]

C = [A,B]
C[0] > C[1]

print(B)

167627228653835780533306798789391434121746937938178456823521266766618700274968871486579197384017519965197737321774692151064825152318481088987488196619282527853678614081685983479367010937281916937789779604984825323634847116013276842617203624285657812177082858998034176534095913889454739662019244356068708344631165145684339379622633892483062434806650124047832194252799569209638806849844181440427417069901198463603117101092590092061475915810535826287372166671269264958415223056517944179449209403217531682945836947861392172035029893686466856662209031273687231348943157653862360896794385335194152651555161643502345149624309582815800929127431850339477961135084947719701760915885284925269480312832347348340430906192620961854776824653177572125031571289471717740314506340389612104698419413441691830575772257222261774615576576

A_answer =  58895511070282323759226869401194540798921127740389888180633114320468193287313782370557803287388787830606682961263541866906740554445580807631109170551393994207914164026532178849065645616091449417420501917069655760101169817548113715717263057548604958479390493460115868699054667270795776555980093831165264003942016861991315908363039501899315253843509936776952828375241926180206795526116728003105757149508891529723072393655538816331606430534887417309156737687629256498726606357043714123412226153060432100988855451342366746188596611261795311537996588353922399817045234558953550492641755372962505682861315153642356599085933096084423716175609569247233023879428902077083096302220594951714054198377707152921921134981253684548381195174819056735442682629924742369662414360968830469478731968837021730911202213535705481496039737482197919131364081461935702623537938691297394256512330644586447057842914355582664355052257312095647052787216441179365139974299820314217789731462877876066914942151175764917198853870762422067786688086213159115579573862617444711347286894585358416795136383909338026896634842943284309368806241569249432116225257474097663056468702200961730103666071411876881408101821886755299005576032499890619146944340071987567287372668366459109180086087152891430916604643410770546902711024104434309756612107715983866044446533085890738899583146032330585519022347879808812005805115174526570906414078969238114952783514246844141120857470729749864005420731175512221537799691010822507582508072359825850920079016505526935684788825330744778031371970021500480965981433251636469183199176982773342957271917175993634658286774916084949784769122426351099305519298987616381735868556528832709064390057433211808613037295742987034533852502561776410978504872532812347615164610758576223538479439398034226320140444086435842540607404882038789465788064709652631435425067831708832646695205361450466871187353202353674037432470494790926711773918814025327050771240918136280173566639124586046763523627974266248724948916519832899579877839366945120905509437302079917813222023964475108642027937485388524185895925148644055199506903478971327393239630707280218076414317762745753416361360213853367349901175736369717399049568374980593304269013357943019982428720456479290729365750249893405451468713615660528604405796560932823464337610727217657890888382345533399233765279361114927638541602741870063878168814384279548240337528296261708929177985221879065791453091848624243831019260585827731106116763961792059343452798075695303976977658531631774221209254059050826923834975429568306924670411392262390804571280464301622570830445566347131923701540002356769974070625073992223924876676854229571161373066541491407425367571692250682993099001276046686906103405812314703485861929026378173082273487689870917606184653419258920777612148828163540769500200558637868740178217850150894711636688488502883527198747720197592666424986641761181740019678211741267148399229852717218532976750713871971228939718391462538219911011713919264904077234710859311246517642603776344370380877901600142004514415428948901224357571511893357052612448252872308739405553549528465110540975207405459424219984358796571872386473686254628938200078516330878131652425601675855797450469702491277170735437589945389289076540355872727134127849368968949223033762200677608474785666239261448049886870700243996169962787821191918945581410858895375842800078653343593150058216912946203328520452398186855672317357399710605982540551327726778854401228351024395281572641521861612539268919192720439549732186141991712442185718095479117919300508241983192341651647418918401398573695137084964504335876545251738193403252936758375560194024827327746034899462176451516182387874732279956284880144333449556809630720683000729024606955797165850838828642830526732745552208657399712574796104147071813000577261825093584752450059899709265087696641369336014553363389417222527741240327400257972605767904460403429001379196224908116290012311760135028667780900768344525440776242489235732004597070086310624014358626338087271152492095295263259655728846202533960209382745692802718928132370840088563673585493973526003665721352226440426336397820802197863129406248148582948970280887236419841152238186016885677833950622135237843303665735124692739814446981985198895639802911013270508516268736623950876086647234711137837754612961345030819398874499893832914704588254782234476701768595558259345481759631388738865760527831707193966602717484644691436240944235481222216588738845539655922672718781494685866565381206210877759722403362239177444211038692839075200537769263755215804679861834439805816761270045814014465083485065289949396349732903922374590365588649388286657984085711472874178869826134496767788068546817560148822395965893876319705853589768410466748283942107783039843733110334619964347395624045458040804526004637709535705982344456249316446981152717128426372983414779303864813855404244273306780707161416670303716667192922165637836237393810155065747948401416677168921347704653131462973613364582255505308814368033858974937027551130205761260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B_answer = 167627228653835780533306798789391434121746937938178456823521266766618700274968871486579197384017519965197737321774692151064825152318481088987488196619282527853678614081685983479367010937281916937789779604984825323634847116013276842617203624285657812177082858998034176534095913889454739662019244356068708344631165145684339379622633892483062434806650124047832194252799569209638806849844181440427417069901198463603117101092590092061475915810535826287372166671269264958415223056517944179449209403217531682945836947861392172035029893686466856662209031273687231348943157653862360896794385335194152651555161643502345149624309582815800929127431850339477961135084947719701760915885284925269480312832347348340430906192620961854776824653177572125031571289471717740314506340389612104698419413441691830575772257222261774615576576

A == A_answer

True

B == B_answer

True

A == B_answer

False