Introduction to Python                 Abhinav Upadhyay           <abhinav@socialtwist.com>
What is Python●   A dynamically typed, object oriented    programmnig language●   Created by Guido van Rossum in 1989
Features●   High-level●   Object Oriented●   Scalable●   Extensible●   Portable●   Readable●   Managed runtime●   Interpre...
Difference from C Style Languages●   Forget ; and {}●   Embrace indentation
Getting Started●   “Hello, World” in Python:        print Hello, world!
Getting Started●   Redirecting your output        file = open(output, w)        print >> file, Hello, world!
Making your program interactive●   Getting user input:        name = raw_input(Enter your name: )        print name
Comments in Python●   Single line comments --> #●   Multiline comments -->  your comment ●   Docstrings
Operators●   Numerical operators: +, -, /, //, *, **, %●   Comparision operators: <, >, <=, >=, ==, !=, <>●   Logical oper...
Numerical types in Python●   int    –     long    –     float●   bool●   complex
String handling in Python●   Creating a string:         my_string = “this is a string”         my_2nd_string = string usin...
String handling in Python●   String operators:        + --> Performs concatenation              str1 = a              str2...
String handling in Python●   String operators:        % --> Format operator              age = 20              str1 = Your...
String handling in Python●   String Manipulation:    –   Indices starting from 0    –   Indices from last element starting...
String handling in PythonSlicing:  ●   Use the slicing operator [] to slice the string into smaller      parts  ●   Syntax...
Built-in functions of Python●   Functions which are built-in to the Python    interpreter and are always available●   Exam...
Common Python Data-Structures●   Lists:    –   Array like data-structure    –   Objects stored in sequential order    –   ...
Common Python Data-Structures●   Tuples:    –   Similar to lists, with two visible differences:         ●   Lists use [], ...
Common Python Data-Structures●   Dictionaries:    –   Hash tables    –   Can store any number of objects    –   {} are use...
Loops in Python●   For loop:      Used for iterating over a sequence of items      for item in list:        print item
Loops in Python●   While loop:      Used for executing a suite of code a number      of times.      Count = 0      while c...
Conditionals●   If-elif-else      if <condition>:         #statement1         #statement2      elif <condition 2>:        ...
File handlingF = open(file1.txt, r)for eachLine in F:  print FF.close()f = open(file2.txt, w)f.write(hello, worldn)f.close()
Functions in Python●   The def keyword●   The return value●   Returning multiple values
Python intro
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Python intro

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A rough presentation on the basics of Python, which I gave to my team at SocialTwist.

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Python intro

  1. 1. Introduction to Python Abhinav Upadhyay <abhinav@socialtwist.com>
  2. 2. What is Python● A dynamically typed, object oriented programmnig language● Created by Guido van Rossum in 1989
  3. 3. Features● High-level● Object Oriented● Scalable● Extensible● Portable● Readable● Managed runtime● Interpreted and Byte-compiled.
  4. 4. Difference from C Style Languages● Forget ; and {}● Embrace indentation
  5. 5. Getting Started● “Hello, World” in Python: print Hello, world!
  6. 6. Getting Started● Redirecting your output file = open(output, w) print >> file, Hello, world!
  7. 7. Making your program interactive● Getting user input: name = raw_input(Enter your name: ) print name
  8. 8. Comments in Python● Single line comments --> #● Multiline comments --> your comment ● Docstrings
  9. 9. Operators● Numerical operators: +, -, /, //, *, **, %● Comparision operators: <, >, <=, >=, ==, !=, <>● Logical operators: and, or, not
  10. 10. Numerical types in Python● int – long – float● bool● complex
  11. 11. String handling in Python● Creating a string: my_string = “this is a string” my_2nd_string = string using single quotes my_3rd_string = triple quotes also work
  12. 12. String handling in Python● String operators: + --> Performs concatenation str1 = a str2 = b print a + b Output: ab * --> Performs repitition str1 = a print a * 5 Output: aaaaa
  13. 13. String handling in Python● String operators: % --> Format operator age = 20 str1 = Your age is %dn % age Output: Your age is 20
  14. 14. String handling in Python● String Manipulation: – Indices starting from 0 – Indices from last element starting with -1 str1 = hello, world print str1[0] Output: h print str[-1] Output: d Print str[-2] Output: l
  15. 15. String handling in PythonSlicing: ● Use the slicing operator [] to slice the string into smaller parts ● Syntax: str[m:n] – This will print the characters of the string starting from the mth position till the nth position (but excluding the nth character) str1 = 0123456789 print str1[1:4] Output: 123
  16. 16. Built-in functions of Python● Functions which are built-in to the Python interpreter and are always available● Examples: pow(), print(), open(), int(), str(), etc.● Some useful BIFs: – type(), help(), dir()
  17. 17. Common Python Data-Structures● Lists: – Array like data-structure – Objects stored in sequential order – Indices starting from 0 – Can store arbitrary number of objects (unlike fixed length arrays in other languages) – Can also store objects of different types in the same list.
  18. 18. Common Python Data-Structures● Tuples: – Similar to lists, with two visible differences: ● Lists use [], while tuples use () in their syntax ● Tuples are immutable data-structures
  19. 19. Common Python Data-Structures● Dictionaries: – Hash tables – Can store any number of objects – {} are used for creating dictionaries
  20. 20. Loops in Python● For loop: Used for iterating over a sequence of items for item in list: print item
  21. 21. Loops in Python● While loop: Used for executing a suite of code a number of times. Count = 0 while count < 10: print count count += 1
  22. 22. Conditionals● If-elif-else if <condition>: #statement1 #statement2 elif <condition 2>: #statement3 #statement4 else: pass
  23. 23. File handlingF = open(file1.txt, r)for eachLine in F: print FF.close()f = open(file2.txt, w)f.write(hello, worldn)f.close()
  24. 24. Functions in Python● The def keyword● The return value● Returning multiple values
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