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Current state

Current state. C and Assembly – Efficient code with access to OS services Shell Scripts – connecting Unix utilities by I/O redirection and pipes. Glue language. In practice, programs output needs pre-processing Usually an interpreted scripting language Useful for writing and maintaining:

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Current state

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  1. Current state • C and Assembly – Efficient code with access to OS services • Shell Scripts – connecting Unix utilities by I/O redirection and pipes

  2. Glue language • In practice, programs output needs pre-processing • Usually an interpreted scripting language • Useful for writing and maintaining: • custom commands for a command shell • wrapper programs for executables • C/Java VS. Python

  3. Example import java.io.IOException;import java.io.FileReader;import java.io.BufferedReader;class numlines { public static void main(String[] args) throws IOException {BufferedReaderinp = new BufferedReader(new FileReader(args[0])); String line; for(inti=1;;++i) { line = inp.readLine(); if(line==null) break;System.out.printf("%3d: %s\n", i, line); }inp.close(); }} ------------------------------------------------------------------------------------------- import sysi = 1for line in file(sys.argv[1]): print "%3d: %s" % (i, line),i+= 1

  4. Python • An open source interpreted programming language • High-level language • Object-Oriented • Functional Programming • Suitable for scripting • Practical ( VS. Efficiency ) • Dynamic language

  5. Variables • No need to declare • Not typed greeting = "hello world" greeting = 12**2 print greeting • Need to assign (initialize) • use of uninitialized variable raises exception

  6. Strings • "hello"+"world" "helloworld" # concatenation • "hello"*3 "hellohellohello" # repetition • "hello"[0] "h" # indexing • "hello"[-1] "o" # (from end) • "hello"[1:4] "ell" # slicing • len("hello") 5 # size • "hello" < "jello" 1 # comparison • "e" in "hello" 1 # search

  7. Lists [<elements>] >>> my_list = ['Hello', 1, 2.2, 'world'] >>> len(my_list) 4 >>> my_list[0] ‘Hello’ >>>my_list.append(‘espl’) >>> my_list>>> ['Hello', 1, 2.2, 'world‘,’espl’] >>> delmy_list[0] [1, 2.2, 'world‘,’espl’] >>> my_list.index(‘espl’) >>> 4 >>> ‘espl141’ inmy_list >>> False

  8. Dictonary • Hash tables, "associative arrays" • d = {"duck": "eend", "water": "water"} • Lookup: • d["duck"] -> "eend" • d["back"] # raises KeyErrorexception • Keys, values, items: • d.keys() -> ["duck", "back"] • d.values() -> ["duik", "rug"] • d.items() -> [("duck","duik"), ("back","rug")] • Presence check: • d.has_key("duck") -> 1; d.has_key("spam") -> 0

  9. Tuples • key = (lastname, firstname) • point = (x, y, z) # parentheses optional • a,b,c= point # unpack • lastname = key[0] • sort of an immutable list • key[1] = ‘Abed’ #TypeError: 'tuple' object does not support item assignment

  10. Functions def<function_name>(<arguments>): <body> def factorial(n):fact = 1 foriin range(1, n): fact = fact * i returnfact

  11. Classses class student: def__init__(self, id): self._id = id self._grades = {} defupdate_grade(self, subject, grade): self._grades[subject] = grade #Comment, Main: s = student('233445598') s.update_grade('heshbon', 80) s.update_grade('handasa', 49)

  12. Modules >>> from math import * >>> sin(30*3.14/180) >>> from math import sin >>> sin(30*3.14/180) >>> from math import sin as sinus >>>sinus(30*3.14/180)

  13. And More … • Control structures • If statement • While • For • ….

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