Python intro

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

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

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Transcript

  • 1. Introduction to Python Abhinav Upadhyay <abhinav@socialtwist.com>
  • 2. What is Python● A dynamically typed, object oriented programmnig language● Created by Guido van Rossum in 1989
  • 3. Features● High-level● Object Oriented● Scalable● Extensible● Portable● Readable● Managed runtime● Interpreted and Byte-compiled.
  • 4. Difference from C Style Languages● Forget ; and {}● Embrace indentation
  • 5. Getting Started● “Hello, World” in Python: print Hello, world!
  • 6. Getting Started● Redirecting your output file = open(output, w) print >> file, Hello, world!
  • 7. Making your program interactive● Getting user input: name = raw_input(Enter your name: ) print name
  • 8. Comments in Python● Single line comments --> #● Multiline comments --> your comment ● Docstrings
  • 9. Operators● Numerical operators: +, -, /, //, *, **, %● Comparision operators: <, >, <=, >=, ==, !=, <>● Logical operators: and, or, not
  • 10. Numerical types in Python● int – long – float● bool● complex
  • 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. 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. String handling in Python● String operators: % --> Format operator age = 20 str1 = Your age is %dn % age Output: Your age is 20
  • 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. 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. 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. 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. 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. Common Python Data-Structures● Dictionaries: – Hash tables – Can store any number of objects – {} are used for creating dictionaries
  • 20. Loops in Python● For loop: Used for iterating over a sequence of items for item in list: print item
  • 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. Conditionals● If-elif-else if <condition>: #statement1 #statement2 elif <condition 2>: #statement3 #statement4 else: pass
  • 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. Functions in Python● The def keyword● The return value● Returning multiple values