1 *Script |
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4 *Hello and welcome to this tutorial on Basic Python using Python. |
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6 This tutorial formally introduces Python as a language . Through this tutorial we will be able to understand Basic Data types like number , Boolean and strings .Some basic operators , simple input/output and basic conditional flow . |
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7 |
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8 In numbers Python supports three kinds of data types , |
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9 |
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10 floats,integers and complex numbers |
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11 |
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12 An integer can be defined as follows : |
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13 a=13 |
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15 This make a an integer variable with value 13 . |
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17 You can also type 9 around 20 times |
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19 a=99999999999999999999999 . as you can see Python does not have a limit on how long an integer has to be . Isn't that great . |
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20 |
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21 Now will try a float. |
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22 |
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23 let's type |
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24 p=3.141592 if you type out p now you will notice that it is not absolutely equal to p you typed in . The reason for that is how a computer saves decimal values . |
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25 |
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26 Apart from integer and float, Python has an in-built support for complex numbers. Now we try to assign a complex value to a variable . |
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27 Type: |
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28 c = 3+4j |
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29 As you can see ,the notation for complex numbers is similar to the one used in electric engineering. |
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30 We will now try some operations on complex numbers . First we will try to get the absolute value of the complex number . For this we will use the abs built in function . For this do : |
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31 abs in parenthesis c . |
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32 |
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33 Do get the imaginary part of c you can do : |
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34 |
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35 c.imag |
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36 |
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37 and similarly for real part do : |
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38 |
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39 c.real |
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40 |
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41 Python also has Boolean as a built-in type . |
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42 |
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43 Try it out just type .. |
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44 t=True , note that T in true is capitalized . |
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45 |
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46 You can apply different Boolean operations on t now for example : |
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48 |
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49 f=not t , this saves the value of not t that is False in f. |
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50 |
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51 We can apply other operators like or and and , |
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52 |
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53 f or t gives us the value True while |
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54 f and t gives us the value false. |
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55 |
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56 You can use parenthesis for precedence , |
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57 |
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58 Lets write some piece of code to check this out . |
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59 |
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60 a=False |
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61 b=True |
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62 c=True |
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63 |
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64 To check how precedence changes with parenthesis . We will try two expressions and their evaluation. |
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65 |
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66 do |
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67 (a and b) or c |
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68 |
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69 This expression gives the value True |
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70 |
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71 where as the expression a and (b or c) gives the value False . |
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72 |
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73 Now we will have a look at strings |
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74 |
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75 type |
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76 w="hello" |
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77 |
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78 w is now a string variable with the value "hello" |
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79 |
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80 printing out w[0] + w[2] + w[-1] gives hlo if you notice the expression for accessing characters of a string is similar to lists . |
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81 |
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82 Also functions like len work with strings just like the way they did with lists |
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83 |
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84 Now lets try changing a character in the string in the same way we change lists . |
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85 |
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86 type : |
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87 w[0]='H' |
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88 |
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89 oops this gives us a Type Error . Why? Because string are immutable . You can change a string simply by assigning a new element to it . This and some other features specific to string processing make string a different kind of data structure than lists . |
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90 |
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91 Now lets see some of the ways in which you can modify strings and other methods related to strings . |
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92 |
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93 Type : |
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94 |
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95 a = 'Hello world' |
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96 |
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97 To check if a particular string starts with a particular substring you can check that with startswith method |
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99 a.startswith('Hell') |
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101 Depending on whether the string starts with that substring the function returns true or false |
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102 |
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103 same is the case a.endwith('ld') |
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104 |
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105 a.upper() |
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106 returns another string that is all the letters of given string capitalized |
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107 |
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108 similarly a.lower returns all small letters . |
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109 |
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110 Earlier we showed you how to see documentations of functions . You can see the documentation of the lower function by doing a.lower? |
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111 |
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112 You can use a.join to joing a list of strings to one string using a given string as connector . |
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113 |
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114 for example |
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116 type : |
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117 ', '.join(['a','b','c']) |
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119 In this case strings are joined over , and space |
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120 |
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121 Python supports formatting values into strings. Although this can include very complicated expressions, the most basic usage is to insert values into a string with the %s placeholder. %d can be used for formatting things like integers and %f for floats |
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124 Their are many other string formatting options you can look at http://docs.python.org/library/stdtypes.html for more information on other options available for string formatting. |
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127 Operators ---- Probably can be a different chapter . |
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129 We will start the discussion on operators first with arithmetic operators . |
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130 |
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131 % can be used for remainder for example |
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133 864675 % 10 gives remainder 5 |
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135 |
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136 you can use 2 *'s for power operation |
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138 for example 4 ** 3 gives the result 64 |
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139 |
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140 One thing one should notice is the type of result depends on the types of input for example : |
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141 |
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142 17 / 2 both the values being integer gives the integer result 2 |
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143 |
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144 however the result when one or two of the operators are float is float for example: |
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145 |
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146 17/2.0 |
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147 8.5 |
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148 17.0/2.0 |
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149 8.5 |
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