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diff --git a/cond-loops.org b/cond-loops.org deleted file mode 100644 index aaa887b..0000000 --- a/cond-loops.org +++ /dev/null @@ -1,145 +0,0 @@ -* Control statements -*** Outline -***** Introduction -******* What are we going to do? -******* How are we going to do? -******* Arsenal Required -********* working knowledge of arrays - -*** Script - Welcome. - - In this tutorial we shall be covering conditional statements and - control loops. We have used them already in some of our previous - sessions with brief introduction. We shall be covering 'if-else' - statement, 'while' and 'for' statements formally. - - - For understanding of if-else statement we will write a python - script that takes a number as input from user and prints 0 if it is zero - and prints "Be positive" if it is negative, prints "Single" if the input is 1 - and if the number is not 0 or 1 or negative, it prints "More". - - To write the program, open Scite text editor by going to Applications-> - Programming->Scite: - - First we prompt user for entering a integer by using raw_input - str_x = raw_input("Enter an integer: ") - since we know raw_input gives string, we convert the input string to an integer - by typing - x = int(str_x) - - now we check if the number is less than zero. - type - if x < 0: - Please not - #if number is negative we have to print "Be positive" - #so we give four spaces for indentation and type - print 'Be positive!' - - elif x == 0: - to check if the number is equal to zero - #This is else-if condition - print 'Zero' - elif x == 1: - print 'Single' - then we type the else statement which gets executed when all the if and elif statements fail - so type - else: - print 'More' - - Save this script by going to file menu and clicking on save. - save it in home folder with name 'ladder.py' - - let us check the program on ipython interpreter for various inputs - open ipython terminal and type - %run ladder.py - It will prompt us to enter a integer and based on our input it - prints appropriate message. - - We can use binary operators like and/or/not to check for multiple - conditions. - - Python supports only if-elif-else conditional constructs, - switch-case statements are not available/supported in Python. - - Now lets look at loop constructs available. Python supports 'while' - and 'for' statements. - - To understand the while we shall write a script that prints all the fibonacci - numbers less than 10. In fibonacci series the sum of previous two elements - is equal to the next element. - - In Scite go to file menu and click on new and it opens a new tab. - - First we initialize two variable to first and second number of - series - a, b = 0, 1 - while b < 10: - This block will be executed till this condition holds True - print b, - Note ',' here for printing values in one continues line. - a, b = b, a+b - This is one powerful feature of Python, swapping and assigning - new values at the same time. After this statement a will have - present 'b' value and b will have value of 'a+b'(phew this can be close) - - Save this file as 'fabonacci.py' and lets run it from IPython - interpreter by - %run fabonacci.py - - 'for' in python works any kind of iterable objects. In our - previous sessions we used 'for' to iterate through files and lists. - - So we are going to use for loop print the squares of first five whole numbers. - - To generate squares, we have to iterate on list of numbers and we are - going to use the range function to get the list of numbers. - - let us look at the documentation of range function by typing - range? - we see that it takes three arguments, first is the start/initial value - second one is the stop/last value and third is the step size. - - Out of these, 'start' and 'step' arguments are optional. - - So to get list of first five natural numbers, we use - range(5) - - Note here that last/stop value is not included in resulting list. - - So to get square of first five number all we have to do is - iterate over this list. - for i in range(5): - ....print i, i*i - .... - .... - - Similarly to get square of all odd numbers from 3 to 9 we can do - something like - - for i in range(3, 10, 2): - so the list returned from range this time will start from 3 and - end at 10(excluding it) with step size of 2 so we get odd numbers - only - ....print i, i*i - .... - .... - - since the for statement in python works on any iterable we can also iterate through strings - - to print each character in a string we do - for c in "Guido Van Rossum": - print c - - we see that it prints all the characters one by one - - That brings us to the end of this tutorial. We have learnt - conditional statements in Python. How to write loops - using 'while' statement. Range function and using for loop - - - Thank you! - -*** Notes - |