mysqlimport from text file

# Import multiple txt files into MySQL DB 

# Table name is txt file name (no need to mention)

# We will be using /data as the reference directory

#sudo mkdir -p /data

#sudo su - root

cd /data

#git clone https://github.com/dgadiraju/nyse_all.git

#gunzip /data/nyse_all/nyse_data/

# Each file soft link to stock_eod.txt

# stock_eod acts as Table Name

for f in /home/cloudera/data/nyse/nyse_all-master/nyse_data/*.txt

do

  echo '------------'

  echo $f

  sudo unlink stock_eod.txt

  sudo ln -s $f stock_eod.txt

  sudo mysqlimport \

    --host=127.0.0.1 \

    --user=root \

    --password=cloudera \

    --fields-terminated-by=',' \

    --lines-terminated-by='\n' \

    --local \

    --lock-tables \

    --verbose \

    nyse stock_eod.txt

echo "Done: '"$f"' at $(date)"

done

bigdata, hdfs

• Hdfs commands
• hadoop fs -ls <>
• hadoop fs -mkdir <>
• hadoop fs -rmdir <>
• Copy file from Edge Node to HDFS
• hadoop fs -put /home/cloudera/<src> /user/cloudera/<dest> 
• Read file rom HDFS
• hadoop fs -cat /user/cloudera/<file_path>
• hadoop dfsadmin -safemode leave

✓ -R : Recursively list the contents of directories.

✓ -C : Display the paths of files and directories only.

By default it sorts in ascending order by name.

✓ ls –r : Reverse the order of the sort.

✓ ls –S : Sort files by size.

✓ ls –t : Sort files by modification time (most recent first).

✓ Command : rmdir

• Remove Directory if it is empty.

• --ignore-fail-on-non-empty : Suppress Error messages if the Folder you are trying to remove is non empty.

✓ Command : rm

• rm remove files.

• With option –r , recursively deletes directories

• With option –skipTrash bypasses trash, if enabled.

• With option –f, no error message even if file does not exist. Check with Unix command $?. It returns the status of

last ran job. 0 means successful and 1 means not successful.

✓ Command: mkdir

• Create Directory

• –p : Do not fail if the directory already exists. Also we can create multiple folders recursively.

HDFS to Local

###########

✓ Command - copyToLocal or get

hadoop fs -get practice/retail_db/orders .

✓ Error if the destination path already exists. To overwrite use –f flag.

hadoop fs -get practice/retail_db/orders .

hadoop fs -get –f practice/retail_db/orders .

✓ -p flag to preserves access and modification times, ownership and the mode.

hadoop fs -get -p practice/retail_db/orders .

✓ To Only copy the files with out folder use a pattern.

hadoop fs -get practice/retail_db/orders/* .

✓ When copying multiple files, the destination must be a directory.

mkdir copyHere

hadoop fs -get practice/retail_db/orders/* practice/sample.txt copyHere

Local to HDFS

######

✓ Command - copyFromLocal or put

hadoop fs -mkdir –p practice/retail_db

hadoop fs -put dataFiles/* practice/retail_db/

hadoop fs -mkdir –p practice/retail_db1

hadoop fs -put dataFiles practice/retail_db1/ #Creates a subfolder dataFiles under retail_db

✓ Error if the destination path already exists. To overwrite use –f flag.

hadoop fs -put -f dataFiles/* practice/retail_db/

✓ -p flag to Preserves timestamps, ownership and the mode.

hadoop fs -put -p dataFiles/* practice/retail_db/

✓ We can also copy multiple files.

hadoop fs -put -f dataFiles/* sample.txt practice/retail_db/

✓ First 10

hadoop fs -cat practice/retail_db/orders/part-00000 | head -10

✓ Last 10

hadoop fs -cat practice/retail_db/orders/part-00000 | tail -10

Statistics

#########

✓ Command – stat

• Print statistics related to any file/directory

✓ default or %y - Modification Time

hdfs dfs -stat %y <hdfs_file_name>

✓ %b - File Size in Bytes

hdfs dfs -stat %b <hdfs_file_name>

✓ %F - Type of object.

✓ %o - Block Size

✓ %r - Replication

✓ %u - User Name

✓ %a - File Permission in Octal

✓ %A - File Permission in Symbolic

storage details in HDFS

##############

✓ Command – df

• Shows the capacity, free and used space of the HDFS file system.

• hadoop fs -df

• -h →Readable Format

✓ Command – du

• Show the amount of space, in bytes, used by the files that match the specified file pattern.

• hadoop fs -du practice/retail_db

• -h :Readable Format

• -v : Displays with Header

• -s : Summary of total size

File Metadata

########

✓ Command – fsck

✓ Even if a Size of a file has less than 128MB , it will still occupy 1 Block.

✓ Help: hadoop fsck –help

### Print the fsck High Level Report

hadoop fsck practice/retail_db

### -files → Print a detailed file level report.

hadoop fsck practice/retail_db –files

### -files -blocks →Print a detailed file and block report.

hadoop fsck practice/retail_db –files -blocks

### -files -blocks -locations → Print out locations for every block

hadoop fsck practice/retail_db –files –blocks –locations

### -files -blocks -racks → Print out network topology for data-node locations

Properties update (-D)

How to handle carriage return

Vim - view in binary mode

file rest.py

# rest.py: Python script, ASCII text executable, with very long lines, with CRLF line terminators

vim -b rest.py  # to  view ^M characters

Solution

1) dos2unix rest.py

2) Alternate to dos2unix

sed -i -e "s/\r//g" `cat /tmp/file_changes.txt`

-i: in-place

-e: regular expression

\r: escaped carriage return

/g: replace globally

Git

• vim .git/config
• [core]
• autocrlf = true
• filemode = false
• git diff --ignore-space-at-eol > /tmp/complete_diff.txt

Python3 write to file using Print

New version

with open(f'output.csv', 'w') as f:

      print(data, file=f)

Old version

with open(f'output.csv', 'w') as f:

      f.write(data)

Python3 fstrings

vars = 'abc'

print(f 'Variable  is : {vars}')

This is much better than 'Variable is : {}'.format(vars)

How to change the MySQL root account password on CentOS7?

 

1. Stop mysql:

systemctl stop mysqld

2. Set the mySQL environment option 

systemctl set-environment MYSQLD_OPTS="--skip-grant-tables"

3. Start mysql usig the options you just set

systemctl start mysqld

4. Login as root

mysql -u root

5. Update the root user password with these mysql commands

mysql> UPDATE mysql.user SET authentication_string = PASSWORD('MyNewPassword') WHERE User = 'root' AND Host = 'localhost';

mysql> FLUSH PRIVILEGES;

for 5.7.6 and later, you should use 

mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'MyNewPass';

mysql> quit

6. Stop mysql

systemctl stop mysqld

7. Unset the mySQL envitroment option so it starts normally next time

systemctl unset-environment MYSQLD_OPTS

8. Start mysql normally:

systemctl start mysqld

Try to login using your new password:

7. mysql -u root -p

EC2 - Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

• EC2 login Issue
• ssh -i /root/stage.pem root@ec2-54-<>.compute-1.amazonaws.com
• ERROR
• EC2 - Permission denied (publickey,gssapi-keyex,gssapi-with-mic).

• Reason
• There is a chance PEM file not added to ~/.ssh/authorized_keys 

Solution

• Go to EC2 Dashbaord
• Click on Connect (EC2 Instance Connect)

• Open ~/.ssh/authorized_keys
• Add the entry
• ssh-rsa AAAAB3NzaC1yc2EAAAA<....>nJXw== Staging
• Try to SSH again
• Done

systemctl chkconfig - Enable/Disable service on boot

chkconfig --list httpd

chkconfig --list varnish

(or)

systemctl list-unit-files | grep httpd

systemctl list-unit-files | grep varnish



systemctl is-active httpd

systemctl is-active varnish


Enable on boot

• chkconfig httpd on

Disable on boot

• chkconfig httpd off

Find Unix Distribution Version

• cat /proc/version
• Linux version 4.14.219-164.354.amzn2.x86_64 (mockbuild@ip-10-0-1-103) (gcc version 7.3.1 20180712 (Red Hat 7.3.1-12) (GCC)) #1 SMP Mon Feb 22 21:18:39 UTC 2021 
• rpm -E %{rhel}
• 7

Python Array Vs List

 Python Array Vs List

List	Array
Heterigenous elements E.g, [1, 2, [3, 4], 5, 6]	Homogenous elements numbers = array.array('i', [1, 2, 3]) Explicitly define type of elements while defining (i - means integers
Use lot more space	Use less spcace compared lists
List contains pointers to different objects	Like C language arrays, with a pointer pointing to first element & rest are allocated in continuous memory
More flexible keeping different structures of data	Less flexible
Less efficient in storing & manipulating	More efficient in storing & manipulating
Used when your collection grow & shrink in time efficient manner & manage lot of data types in a list	Used when you perform lot of computationally intensive math operations
	Numpy arrays are more suited for mathematical operations

Python Arrays

Arrays are sequence of homogeneous elements

import array

numbers = array.array('i', [1, 2, 3])

numbers.append(4)
print(numbers) # array('i', [1, 2, 3, 4])

# extend() appends iterable to the end of the array
numbers.extend([5, 6, 7])
print(numbers) # array('i', [1, 2, 3, 4, 5, 6, 7])

git merge reset merge

• git fetch && git checkout master
• # You want to pull master to your branch
• git checkout branch1 (from master)
• git merge master (or git pull origin master)
• CONFLICT (content): Merge conflict in site/test.py
• --- say some conflicts & u want to move to master / branch2

• git checkout master
• ----> error: you need to resolve your current index first
• git branch ## branch1
• git reset --merge
• git checkout master # will work

How to evaluate time taken for urls using curl

• Configure ~/.curlrc
• Add file ~/.curlrc & add the below
• -w "dnslookup: %{time_namelookup} | connect: %{time_connect} | appconnect: %{time_appconnect} | pretransfer: %{time_pretransfer} | starttransfer: %{time_starttransfer} | total: %{time_total} | size: %{size_download}\n"
•  How to call urls using Curl?
• curl -so /dev/null "https://www.site.com/test/video.mp4"
• dnslookup: 0.013 | connect: 0.335 | appconnect: 1.090 | pretransfer: 1.090 | starttransfer: 1.666 | total: 24.770 | size: 128750670
• curl -so /dev/null "https://cdn.site.com/test/video.mp4"
• dnslookup: 0.013 | connect: 0.051 | appconnect: 0.311 | pretransfer: 0.311 | starttransfer: 1.287 | total: 11.556 | size: 128750670

We can observe 2nd url (CDN) takes almost half the time as the first once.

Python lamdba filter

result_dict = {
    1: {'site': u'test1.com', 'site_name': u'test1', 'is_https': True},
    2: {'site': u'test2.com', 'site_name': u'test2', 'is_https': False}
        }
print('-' * 30)
print(result_dict)

print('-' * 30)
https_list = dict(filter(lambda x: x if x[1]['is_https'] else None, result_dict.items()))
non_https_list = dict(filter(lambda x: x if not x[1]['is_https'] else None, result_dict.items()))

print(https_list)
print('-' * 30)
print(non_https_list)

Output:

------------------------------
{1: {'site_name': u'test1', 'site': u'test1.com', 'is_https': True}, 

2: {'site_name': u'test2', 'site': u'test2.com', 'is_https': False}}
------------------------------
{1: {'site_name': u'test1', 'site': u'test1.com', 'is_https': True}}
------------------------------
{2: {'site_name': u'test2', 'site': u'test2.com', 'is_https': False}}

DB Tools

• dbeaver (FOSS - Free and Open Source S/W)
• DB Visualizer (Free Tier - Only Read Operations)
• PopSQL

Supervisor in Linux

• Supervisor is a client/server system that allows its users to monitor and control a number of processes on UNIX-like operating systems.
• Start like any other program at boot time.
• If process gets killed, it brings up the program on its own.

Tried these in CentOS (RedHat)

How to install

yum -y install supervisor

How to Start/Restart/Stop/Status

systemctl start supervisord

systemctl enable supervisord

systemctl status supervisord

/etc/supervisord.d/test.ini

[group:test]

programs=test1, test2

[program:test1]

command=python -u test1.py

directory=/opt/site

stdout_logfile=/tmp/prabhath.log

redirect_stderr=true

[program:test2]

command=python -u test2.py

directory=/opt/site

stdout_logfile=/tmp/prabhath.log

redirect_stderr=true

How to restart Group

supervisorctl restart test:*

/opt/site/test1.py

import time

while True:

    print('inside Test1')

    time.sleep(1)

/opt/site/test2.py

import time

while True:

    print('inside Test2')

    time.sleep(2)

How to keep terminal alive

To prevent connection loss, instruct the ssh client to send a sign-of-life signal to the server once in a while. Add the following to ~/.ssh/config

vim ~/.ssh/config

Host *
  ServerAliveInterval 120

AWS Elastic Search

AWS Elastic Search

• Widely adapted open source search engine
• Building real-time custom search engine
• Logging and log analysis
• Scraping and combining multiple data sources
• Event data and metrics (e.g., application clickstream data)
• Kibana UI interface tool for ElasticSearch

Cloud Search

• Fully managed search solution by AWS

AWS Kinesis

AWS Kinesis (3 types)

• Kinesis Streams
• Kinesis Firehose
• Kinesis Analytics

• Kinesis Streams
• Ingest and process streaming data with "custom applications"
• Producers put data into streams
• Consumers consume data and process them (fleet of instances)
• Shard
• It is a basic throughout unit of a stream
• Streaming data is in the form on Shards
• Default retention period is 1 day
• You can keep data till 7 days (168 hrs)
• Kinesis Firehose
• Capture, transform & load streaming data
• Deliver real time data to "AWS destinations" like S3, RedShift, ElasticSearch, Splunk etc.,
• You don't need to write applications or manage resources
• Using Lambda, you can transform data before delivering data
• You can compress/encrypt data there by saving storage cost and increasing security
• Scales automatically
• Kinesis Analytics
• Run SQL queries on Kinesis Streaming data
• Analyze and process streaming data from Kinesis Streaming/Firehose

Kinesis Limitations

• No of shards
• Upto 200
• Upto 500 in some regions
• No hard limit (AWS can lift off if u request)
• Data retention
• 1 day be default
• Upto 7 days
• Hard limit (AWS cannot lift off)
• Write limitations
• Shard throughput - upto 1 MB
• No of transactions - 1000 records/sec
• Read limitations
• One shard can return < 2 MB/sec
• No of transactions: 5 records/shard/sec

Kinesis Vs Kafka Vs SQS

Kinesis	Kafka
Messaging system	Messaging system
Stream/Shard	Topic/Partition
Proprietary	Open Source
No operational overload	Heavy operational overload
Stores upto 7 days (default 1 day)	Can store data indefinitely
Kinesis Client Library	Various Kafka clients
	Log compaction
Kinesis	SQS
Messaging system	Messaging system
AWS	AWS
No operational overload	No operational overload
State tracking by client	State tracking by SQS
Message can be read many times	Processed message is deleted
Unified log/stream processing	Balancing tasks among workers

AWS RedShift

RedShift

• Data Warehouse
• Meant to support OLAP (not OLTP), column oriented and massively parallel scale-out architecture
• OLTP meant to Analytics, aggregation of data
• Master & slave nodes
• It does not require/create indexes, materialised views, thereby faster & uses less data than traditional relational databases
• Supports columnar storage like Parquet, ORC
• But it has dist_key and sort_key
• dist_key
• It is the column on which its distributed on each node
• Rows with same value of this column are guaranteed to be on the same node
• sort_key
• It is the column on which data is sorted on each node
• Only one sort_key is permitted
• RedShift doesn't complain on duplicate data even on primary key
• Advantages
• Faster, since it need not check if primary key already exists or not
• Performance, query optimization
• Disadvantages
• Chances of improper data (duplicate data)
• Its upto the user to send proper data to RedShit, user has to handle the improper data before sending it to RedShift Cluster

1) Create a RefShift cluster

2) Connect to cluster and Create tables 

   (Using SQL Workbench - recommended or any DB visualizer)

   If not use Redshitf Query Editor it self

3) Create an IAM role for Redshift with S3 Read only access

4) Attach IAM S3 role to RedShift

5) Suppose your data is in S3, load your data from S3

  copy dimproduct    #<table_name_from_redshift>

  from 's3://redshift-load-queue-test/dimproduct.csv' 

  iam_role '<IAM Role created in step-3>/RedShift-S3-Role' 

  region 'us-east-1'

  format csv

  delimiter ','

6) Upload huge data as gz files

   sales1.txt.gz, sales2.txt.gz, sales3.txt.gz, sale4.txt.gz

   Instead of creating single files, create one manifest file 

   manifest.txt

         {

          "entries": [

              {"url":"s3://redshift-load-queue-test/sales1.txt.gz", "mandatory":true},

              {"url":"s3://redshift-load-queue-test/sales2.txt.gz", "mandatory":true},

              {"url":"s3://redshift-load-queue-test/sales3.txt.gz", "mandatory":true},

              {"url":"s3://redshift-load-queue-test/sales4.txt.gz", "mandatory":true}

          ]   

         }

  copy factsales    

  from 's3://redshift-load-queue-test/manifest.txt' 

  iam_role '<IAM Role created in step-3>' 

  region 'us-east-1'

  GZIP

  delimiter '|'

  manifest

7) Copy JSON data

   # Json data should not be in a list

   # It should in individual elements

   copy dimdate

   from 's3://redshift-load-queue-prabhath/dimdate.json'

   region 'us-east-1'

   iam_role '<IAM Role created in step-3>/RedShift-S3-Role'

   json as 'auto'

8) Find out any load errors

   select * from stl_load_errors

9) Integrate Kinesis Streaming FireHose to destination as RedShift

    Given the details, Kinesis form this query for you

      COPY firehose_test_table (ticker_symbol, sector, change, price) 

      FROM 's3://redshift-load-queue-<>/stream2020/05/22/04/test-stream-4-2020-05-22-04-19-21-db425054-695f-4fd1-8721-fc07cdeea369.gz' 

      CREDENTIALS 'aws_iam_role='<IAM Role created in step-3>/RedShift-S3-Role'

      JSON 'auto' gzip;

Pandas Tutorial 3

1) Drop Nulls of one column in Pandas

Find isnull in a column:

isnull(master["playerID"]).value_counts()

Output:

False    7520

True      241

Name: playerID, dtype: int64

Drop nulls of specific columns (dropna)

master_orig = master.copy()

master = master.dropna(subset=["playerID"])

master.shape

2) Drop Nulls of multiple column in Pandas

how = 'all' # if all subset cols are nulls

how = 'any' # if any of the subset cols are nulls

df.dropna(subset=[col_list], how='all')

master = master.dropna(subset=["firstNHL", "lastNHL"], how="all")

3)

master1 = master[master["lastNHL"] >= 1980]

master1.shape # (4627, 31)

Vs

master1 = master.loc[master["lastNHL"] >= 1980]

master1.shape # (4627, 31)

But later is good, more performance with huge data

4) filter columns

master.filter(columns_to_keep).head()

(or)

master = master.filter(regex="(playerID|pos|^birth)|(Name$)")

5) Find DF memory usage

df.memory_usage()

def mem_mib(df):

    mem = df.memory_usage().sum() / (1024 * 1024)

    print(f'{mem}.2f Mib')

    

mem_mib(master) # 0.39 MiB

mem_mib(master_orig) # 1.84 MiB

6) Categorical

# A string variable consisting of only a few different values. 

# Converting such a string variable to a categorical variable will save some memory.

def make_categorical(df, col_name):

    df.loc[:, col_name] = pd.Categorical(df[col_name]) 

# to save memory

make_categorical(master, "pos")

make_categorical(master, "birthCountry")

make_categorical(master, "birthState")

7)

pd.read_pickle()

8) Joins

Default is inner join

pd.merge(df1, df2, how='left')

# We joining based on player id of both dfs

# If left df has PlayerId & right df has plrId

pd.merge(df1, df2, left_on='PlayerId', right_on='plrId')

# We joining based on player id of both DFs

# Say if left DF has player id as index

# Here resultant merge DF has index from right DF 

# left DF index (left_index) is not considered in merge dF

pd.merge(df1, df2, left_index=True, right_on='plrId')

# We joining based on player id of both dfs

# Say if right df has player id as index

# Here resultant merge DF has index from left DF 

# right DF index (right_index) is not considered in merge dF

pd.merge(df1, df2, left_on='PlayerId', right_index=True)

# We can even set DF index (set_index) and use

# left_index and right_index 

pd.merge(df1, df2.set_index("playerID", drop=True),

                            left_index=True, right_index=True).head()

# Indicator

# It creates additional column _merge

# It indicates both, left_only, right_only

merged = pd.merge(master2, scoring, left_index=True,

                  right_on="playerID", how="right", indicator=True)

merged["_merge"].value_counts()

both          28579

right_only       37

left_only         0

Name: _merge, dtype: int64

# Filter only right_only

merged[merged["_merge"] == "right_only"].head()

# Filter only right_only or left_only

merged[(merged["_merge"] == "right_only") | (merged["_merge"] == "left_only")].sample(3)

or

# 

merged[merged["_merge"].str.endswith("only")].sample(5)

# Filter out 1:m (one to many)

try:

pd.merge(df1, df2, left_index=True, right_on='plrId', validate="1:m").head()

except Exception as e:

pass

8) Drop random records

df.drop(drop.sample(5).index)

-------

9) Longer to Wider format (pivot)

df.show()

playerID year Goals

10320 hlavaja01 2001 7.0

10322 hlavaja01 2002 1.0

10324 hlavaja01 2003 5.0

15873 markoan01 2001 5.0

15874 markoan01 2002 13.0

15875 markoan01 2003 6.0

18899 nylanmi01 2001 15.0

18900 nylanmi01 2002 0.0

18902 nylanmi01 2003 0.0

# Longer to Wider format conversion

pivot = df.pivot(index="playerID", columns="year", values="Goals")

year 2001 2002 2003

playerID

hlavaja01 7.0 1.0 5.0

markoan01 5.0 13.0 6.0

nylanmi01 15.0 0.0 0.0

pivot = pivot.reset_index()

pivot.columns.name = None

pivot

playerID 2001 2002 2003

0 hlavaja01 7.0 1.0 5.0

1 markoan01 5.0 13.0 6.0

2 nylanmi01 15.0 0.0 0.0

10) Wide to Long format (melt)

# melt()

# Pandas melt() function is used to change the DataFrame format from wide to long.

pivot.melt(id_vars="playerID", var_name="year", value_name="goals")

playerID year goals

0 hlavaja01 2001 7.0

1 markoan01 2001 5.0

2 nylanmi01 2001 15.0

3 hlavaja01 2002 1.0

4 markoan01 2002 13.0

5 nylanmi01 2002 0.0

6 hlavaja01 2003 5.0

7 markoan01 2003 6.0

8 nylanmi01 2003 0.0

-------

Pandas Multi-level Index

1) How to set multi-index

mi = df.set_index(['playerID', 'year'])

mi.head()

2) List multi-index values 

mi.index

MultiIndex([('aaltoan01', 1997),

            ('aaltoan01', 1998),

            ('zyuzian01', 2005),

            ('zyuzian01', 2006),

            ('zyuzian01', 2007)],

           names=['playerID', 'year'], length=28616)

3) len(mi.index.levels) # 2

4) mi.index.levels[0]

Index(['aaltoan01', 'abdelju01', 'abidra01', 'abrahth01', 'actonke01',

       'adamlu01', 'adamru01'], dtype='object', name='playerID', length=4627)

5) mi.index.levels[1]

Int64Index([1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990],

           dtype='int64', name='year')

6) mi.groupby(level="year")['G'].max().head()

year

1980    68.0

1981    92.0

1982    71.0

1983    87.0

1984    73.0

Name: G, dtype: float64

7) idmax (gives index)

mi.groupby(level="year")['G'].idmax().head()

year

1980    (bossymi01, 1980)

1981    (gretzwa01, 1981)

1982    (gretzwa01, 1982)

1983    (gretzwa01, 1983)

1984    (gretzwa01, 1984)

Name: G, dtype: object

8) Filter based on above

mi.loc[mi.groupby(level="year")['G'].idxmax()].head()

firstName lastName pos Year Mon Day Country State City tmID GP G A Pts SOG

playerID year

bossymi01 1980 Mike Bossy R 1957.0 1.0 22.0 Canada QC Montreal NYI 79.0 68.0 51.0 119.0 315.0

gretzwa01 1981 Wayne Gretzky C 1961.0 1.0 26.0 Canada ON Brantford EDM 80.0 92.0 120.0 212.0 369.0

1982 Wayne Gretzky C 1961.0 1.0 26.0 Canada ON Brantford EDM 80.0 71.0 125.0 196.0 348.0

1983 Wayne Gretzky C 1961.0 1.0 26.0 Canada ON Brantford EDM 74.0 87.0 118.0 205.0 324.0

1984 Wayne Gretzky C 1961.0 1.0 26.0 Canada ON Brantford EDM 80.0 73.0 135.0 208.0 358.0

Python 2 Vs 3

Python 2	Python 3
input() may store as int, string raw_input() stores str always	input() function was fixed in Python 3 so that it always stores the user inputs as str
print "Hi" print("Hi")	print("Hi")
3/2 ==> floor(1.5) => 1 (defaults to floor), return int	3/2 ==> 1.5
Strings default stores as Ascii	Strings default stores as unicode Unicode is a superset of ASCII and hence, can encode more characters including foreign ones.
sorted(employees.items(), key=lambda(x,y): y['age'])	sorted(employees.items(), key=lambda x: x[1]['age'])
	AsyncIO
	Fstrings
	It is recommended to use __future__ imports it if you are planning Python 3.x support for your code
xrange() - Lazy evaluation	range() - Lazy evaluation
except NameError, err:	except NameError as err:
my_generator = (letter for letter in 'abcdefg') next(my_generator) my_generator.next()	my_generator = (letter for letter in 'abcdefg') next(my_generator)
print 'Python', python_version() i = 1 print 'before: i =', i print 'comprehension: ', [i for i in range(5)] print 'after: i =', i Python 2.7.6 before: i = 1 comprehension: [0, 1, 2, 3, 4] after: i = 4	Python 3.x for-loop variables don’t leak into the global namespace anymore! print ('Python', python_version()) i = 1 print 'before: i =', i print 'comprehension: ', [i for i in range(5)] print 'after: i =', i Python 3.4.1 before: i = 1 comprehension: [0, 1, 2, 3, 4] after: i = 1
print range(3) print type(range(3)) [0, 1, 2] <type 'list'>	print range(3) print type(range(3)) print(list(range(3))) range(0, 3) <class 'range'> [0, 1, 2]
round(15.5) # 16.0 round(16.5) # 17.0	Bankers rounding round(15.5) # 16 round(16.5) # 16

Python List Vs Array

# Arrays Vs Lists

• Arrays need to be declared. Lists don’t
• Arrays can store data very compactly
• Arrays are great for numerical operations

import array

# Array (stores single data type)

array.array('i', [1, 22, 30, 44, 51]) # integer

array.array('d', [2.5, 3.2, 3.3]) # float

array.array('u', ['a', 'b', 'c']) # unicode

#List

ll = ['abc', 10, ['a', 'b', 'c'], (1,2,3)] # List can store anything 

import numpy as np

# Numpy Array (it can store various data types)

array_2 = np.array(["numbers", 3, 6, 9, 12])

print (array_2)

print(type(array_2))