Difference between revisions of "Python-3.4.3/C2/Getting-started-with-strings/English"
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'''Author: Trupti Kini''' | '''Author: Trupti Kini''' | ||
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{| style="border-spacing:0;" | {| style="border-spacing:0;" | ||
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center> | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <center>'''Visual Cue'''</center> | ||
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* '''Ubuntu Linux 16.04''' operating system | * '''Ubuntu Linux 16.04''' operating system | ||
− | * '''Python 3.4.3''' | + | * '''Python 3.4.3''' and |
* '''IPython 5.1.0''' | * '''IPython 5.1.0''' | ||
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What are Strings? | What are Strings? | ||
− | In '''Python,''' any character within | + | In '''Python,''' any character within '''single/ double/ triple quotes '''is''' '''a''' string.''' |
− | + | ||
− | + | ||
'This is a string' | 'This is a string' | ||
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|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type |
'''a = 'Hello, World!' ''' | '''a = 'Hello, World!' ''' | ||
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|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''x = 'Hello' ''' | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''x = 'Hello' ''' |
'''y = 'World'''' | '''y = 'World'''' | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type | ||
− | '''x | + | '''x ''is equal to''' inside quotes'' '''Hello''' |
Press '''Enter''' | Press '''Enter''' | ||
− | '''y | + | '''y ''is equal to''' inside quotes'' '''World''' |
Press '''Enter''' | Press '''Enter''' | ||
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''z = x + ', ' + y + '!'''' | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''z = x + ', ' + y + '!'''' |
'''print(z)''' | '''print(z)''' | ||
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Now, let us add the two strings. | ||
− | '''z | + | '''z ''is equal to ''x plus''' ''inside quotes'' '''comma plus y plus''' ''inside quotes '''exclamation mark.''''' |
Press '''Enter''' | Press '''Enter''' | ||
− | print ''inside parentheses'' '''z''' | + | '''print''' ''inside parentheses'' '''z''' |
Press '''Enter''' | Press '''Enter''' | ||
− | Here '''x '''and '''y''' are '''string | + | Here '''x '''and '''y''' are '''string variables'''. |
|- | |- | ||
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|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''Hello, World!''' |
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here we can see the output of string concatenation. | ||
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Type '''clear''' |
− | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''. | |
− | + | ||
− | + | ||
− | + | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal | + | |
What if we multiply a string with an integer? | What if we multiply a string with an integer? | ||
Let us find out! | Let us find out! | ||
+ | |- | ||
+ | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> | ||
+ | |||
+ | Press Up arrow till we get '''x''' | ||
− | Recall''' x''' string. | + | Type '''x * 5''' |
+ | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"|Recall''' x''' string. | ||
Press '''Enter''' | Press '''Enter''' | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show Ipython Terminal | ||
− | Highlight | + | Highlight '''HelloHelloHelloHelloHello''' |
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| The '''string''' '''Hello''' is repeated 5 times after '''multiplying'''. | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Pause the video. Try this exercise and then resume the video. | ||
− | + | Obtain the '''string''' as shown without '''typing''' out all the twenty '''hyphens'''. | |
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> Type, |
'''s = "%% " + "-"*20 + "%%"''' | '''s = "%% " + "-"*20 + "%%"''' | ||
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Type, | Type, | ||
− | '''s ''''' | + | '''s ''is equal to''' inside quotes'' '''two percentages ''plus''' inside quotes '''hyphen multiplied by'' twenty ''plus''' inside quotes'' ''' two percentages''' |
Press '''Enter''' | Press '''Enter''' | ||
− | '''print '''''inside parentheses '''''s''' | + | '''print''' ''inside parentheses '' '''s''' |
Press '''Enter''' | Press '''Enter''' | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let's now look at '''accessing''' individual '''elements''' of '''strings'''. | ||
− | We can access individual elements in the '''string''' using the '''subscripts.''' | + | We can access individual '''elements''' in the '''string''' using the '''subscripts.''' |
|- | |- | ||
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Press Up arrow till we get '''a''' | Press Up arrow till we get '''a''' | ||
− | '''<nowiki>a[0] </nowiki>''' | + | '''<nowiki>Type a[0] </nowiki>''' |
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the terminal. | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us clear the '''terminal'''. |
Recall '''a.''' | Recall '''a.''' | ||
− | Press Enter. | + | Press '''Enter'''. |
Type, | Type, | ||
− | '''a '''''inside square brackets zero ''press | + | '''a '''''inside square brackets'' '''zero''' press '''Enter''', gives us the first '''character''' of the '''string'''. |
|- | |- | ||
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where 'n' is the total number of '''characters''' in a '''string'''. | where 'n' is the total number of '''characters''' in a '''string'''. | ||
− | We can '''access''' the '''strings''' from the end using '''negative | + | We can '''access''' the '''strings''' from the end using '''negative indices.''' |
|- | |- | ||
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[IPython Terminal]</nowiki> | ||
− | '''<nowiki>a[-1] </nowiki>''' | + | '''<nowiki>Type a[-1] </nowiki>''' |
− | '''<nowiki>a[-2]</nowiki>''' | + | '''<nowiki>Type a[-2]</nowiki>''' |
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark''' | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''a '''''inside square brackets '''''minus one'' '''''gives us the last '''element''' of the '''string''' i.e. '''exclamation mark''' | ||
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Given a string, '''s''' which is '''Hello World''', what is the output of the following | Given a string, '''s''' which is '''Hello World''', what is the output of the following | ||
− | |||
− | |||
− | |||
− | |||
− | |||
− | |||
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki>Type |
'''s = "Hello World”''' | '''s = "Hello World”''' | ||
'''<nowiki>s[-5]</nowiki>''' | '''<nowiki>s[-5]</nowiki>''' | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal. | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''. |
− | Let us clear the terminal. | + | Let us clear the '''terminal'''. |
Type | Type | ||
− | '''s | + | '''s ''is equal to''' inside quotes'' ''' Hello World '''press '''Enter''' |
− | '''s '''''inside square brackets ''''' | + | '''s '''''inside square brackets '''minus'' five''' gives '''W ''' |
Similarly we will get '''e '''<nowiki>for s[-10].</nowiki> | Similarly we will get '''e '''<nowiki>for s[-10].</nowiki> | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | ||
− | '''<nowiki>s[-15]</nowiki>''' | + | '''<nowiki>Type s[-15]</nowiki>''' |
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. '''Since the string given to us is only 11 '''characters''' long. | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''minus 15''' gives us an '''IndexError. ''' |
+ | |||
+ | |||
+ | Since the string given to us is only 11 '''characters''' long. | ||
|- | |- | ||
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | ||
− | '''<nowiki>s[15]</nowiki>''' | + | '''<nowiki>Type s[15]</nowiki>''' |
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| '''s '''''inside square brackets '''''15 '''again gives '''IndexError '''for the same reason. | ||
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Press Up arrow till we get '''x''' | Press Up arrow till we get '''x''' | ||
+ | Type | ||
'''x<nowiki>[0] = '</nowiki>B'''' | '''x<nowiki>[0] = '</nowiki>B'''' | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Let us attempt to change one of the '''characters''' in a '''string'''. | ||
− | Let us clear the terminal. | + | Let us clear the '''terminal'''. |
Recall '''x''' | Recall '''x''' | ||
− | Press Enter | + | Press '''Enter''' |
Let us manipulate '''x.''' | Let us manipulate '''x.''' | ||
− | '''x '''''inside square brackets '''''zero ''''' | + | '''x ''' ''inside square brackets '' '''zero ''equal to''' inside quotes '' '''B '''press '''Enter''' |
|- | |- | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error? | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Why do we get an error? | ||
− | Initially the value of | + | Initially the value of '''x[0]''' is '''‘H’'''. |
− | + | Now we are trying to assign another value '''‘B’''' to '''x[0]'''. | |
Recall, strings cannot be modified after it is created. | Recall, strings cannot be modified after it is created. | ||
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Show slide '''split()''' and''' join()''' functions |
+ | |||
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions : | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We can split and join the strings by using the functions : | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To join a string, the syntax is | ||
− | '''str ''''' | + | '''str ''dot join''' inside parentheses'' '''sequence''' |
|- | |- | ||
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| <nowiki>[Ipython Terminal]</nowiki> | ||
− | s = “- | + | s = “-” |
− | + | seq = ("a", "b", "c") | |
− | Let us clear the terminal | + | print (s.join( seq )) |
+ | |||
+ | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal'''. | ||
+ | |||
+ | Let us clear the '''terminal''' | ||
Type | Type | ||
− | s ''is equal to inside quotes ''''' | + | '''s ''is equal to''' inside quotes '''hyphen '''''press '''Enter''' |
+ | |||
+ | '''seq ''is equal to''' inside parentheses '' '''a ''comma ''b ''comma '' c '''press '''Enter''' | ||
− | print s ''dot | + | '''print s ''dot'' join''' inside parentheses '''seq '''press '''Enter''' |
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''a-b-c''' |
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c''' | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We will get output as '''a '''''hyphen '''''b '''''hyphen '''''c''' | ||
− | It has joined a, b, c with hyphen. | + | It has joined '''a, b, c''' with '''hyphen'''. |
|- | |- | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| To split a string, syntax is | ||
− | '''str | + | '''str dot split '''''open and close parentheses '' |
|- | |- | ||
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str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( )) | str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( )) | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the terminal | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Switch to the '''terminal''' |
− | + | Type as shown press '''Enter''' | |
+ | |||
+ | |||
+ | '''print str dot split''' ''open and close parentheses'' press '''Enter''' | ||
|- | |- | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Highlight '''['Line1-abcdef', 'Line2-abc', 'Line4-abcd']''' |
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this. | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| We get the output like this. | ||
− | It has split the | + | It has split the strings at '''spaces'''. |
|- | |- | ||
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* Define strings in different ways. | * Define strings in different ways. | ||
* Concatenate strings. | * Concatenate strings. | ||
− | * Print a string repeatedly | + | * Print a string repeatedly and |
* Access individual elements of the string. | * Access individual elements of the string. | ||
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Evaluation | Evaluation | ||
− | # Write code to assign the string | + | # Write code to assign the string ’ is called the apostrophe, to a variable s |
# How will you change s='hello' to s='Hello'. | # How will you change s='hello' to s='Hello'. | ||
− | # The variables s and t are | + | # The variables s and t are strings and r is integer. |
− | s= | + | s=Hello |
− | t= | + | t=World |
r=2 | r=2 | ||
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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve | ||
− | # Write code to assign the string | + | # Write code to assign the string ’ is called the apostrophe, to variable s |
− | # How will you change s ''is equal to '''hello' to s ''is equal to capital | + | # How will you change '''s''' ''is equal to '''hello' to '''s''' ''is equal to capital '''h Hello'. |
− | # The variables s and t are strings and r is integer. | + | # The variables '''s''' and '''t''' are strings and '''r''' is integer. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | + | ||
− | What is the output of s ''multiplied by'' r'' plus'' t ''multiplied by'' r? | + | They are assigned with the values as shown below, |
+ | What is the output of '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r'''? | ||
|- | |- | ||
Line 446: | Line 446: | ||
Solutions | Solutions | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers, | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| And the answers, |
# The given string can be assigned in this manner | # The given string can be assigned in this manner | ||
− | # Strings cannot be manipulated after it is assigned a value | + | # Strings cannot be manipulated after it is assigned a value |
− | + | # The operation '''s''' ''multiplied by'' '''r''''' plus'' '''t''' ''multiplied by'' '''r''' will print each of the two words twice as '''HelloHelloWorldWorld ''' | |
− | # The operation s ''multiplied by'' r'' plus'' t ''multiplied by'' r will print each of the two words twice as '''HelloHelloWorldWorld ''' | + | |
|- | |- | ||
Line 485: | Line 484: | ||
Thank You | Thank You | ||
− | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is | + | | style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.088cm;padding-right:0.191cm;"| This is Trupti Kini from IIT Bombay signing off. |
Thank you. | Thank you. | ||
|} | |} |
Latest revision as of 16:14, 22 January 2018
'Python/C2/Getting Started with Strings/English'Title of script: Getting Started with Strings
Author: Trupti Kini
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containing title, name of the production team along with the logo of MHRD |
Hello Friends. Welcome to the tutorial on "Getting Started with Strings". |
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Objectives |
At the end of this tutorial, you will learn to,
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System Specifications |
To record this tutorial, I am using
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Pre-requisites |
To practise this tutorial, you should know how to
If not, see the pre-requisite Python tutorials on this website. |
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What are Strings? In Python, any character within single/ double/ triple quotes is a string. 'This is a string' “This is a string too” ‘’’This can be a large string’’’ |
What are strings?
In Python, any character within a single/ double/ triple quotes is a string. For example: Single, double, and triple quotes can be used to denote a string as shown here. |
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What are Strings? |
Strings in triple quotes can be written in multiple lines.
We can also define empty strings. String is a collection of characters which cannot be modified after it is created. |
[Terminal]
ipython3 |
Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously.
Type ipython3 and press Enter. |
[IPython console]
%pylab and press Enter. |
Let us initialise the pylab package.
Type %pylab and press Enter. |
[IPython Terminal] Type
a = 'Hello, World!' |
Let us clear the terminal.
We can assign a string to a variable called a. Type a is equal to inside any quotes Hello comma World exclamation mark and Press Enter |
[IPython Terminal] | Now let us learn string concatenation.
Let us assign strings to variables. |
Type x = 'Hello'
y = 'World' |
Type
x is equal to inside quotes Hello Press Enter y is equal to inside quotes World Press Enter |
Type z = x + ', ' + y + '!'
print(z) |
Now, let us add the two strings.
z is equal to x plus inside quotes comma plus y plus inside quotes exclamation mark. Press Enter print inside parentheses z Press Enter Here x and y are string variables. |
Highlight + | The addition operation performs the concatenation of two strings. |
Highlight Hello, World! | Here we can see the output of string concatenation. |
Type clear | Let us clear the terminal.
What if we multiply a string with an integer? Let us find out! |
[IPython Terminal]
Press Up arrow till we get x Type x * 5 |
Recall x string.
Press Enter x multiplied by 5 Press Enter |
Show Ipython Terminal
Highlight HelloHelloHelloHelloHello |
The string Hello is repeated 5 times after multiplying. |
Show Slide
Exercise 1 |
Pause the video. Try this exercise and then resume the video.
Obtain the string as shown without typing out all the twenty hyphens. |
[IPython Terminal] Type,
s = "%% " + "-"*20 + "%%" print(s) |
Switch to the terminal for solution.
Type, s is equal to inside quotes two percentages plus inside quotes hyphen multiplied by twenty plus inside quotes two percentages Press Enter print inside parentheses s Press Enter |
Let's now look at accessing individual elements of strings.
We can access individual elements in the string using the subscripts. | |
[IPython Terminal]
Press Up arrow till we get a Type a[0] |
Let us clear the terminal.
Recall a. Press Enter. Type, a inside square brackets zero press Enter, gives us the first character of the string. |
The indexing starts from 0 and goes up to (n-1).
where 'n' is the total number of characters in a string. We can access the strings from the end using negative indices. | |
[IPython Terminal]
Type a[-1] Type a[-2] |
a inside square brackets minus one gives us the last element of the string i.e. exclamation mark
a inside square brackets minus two gives us the second element from the end of the string i.e. d |
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Exercise 2 s = “Hello World” what is the output of s[-5] s[-10] s[-15] s[15] |
Pause the video. Try this exercise and then resume the video.
Given a string, s which is Hello World, what is the output of the following
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[Ipython Terminal]Type
s = "Hello World” s[-5] |
Switch to the terminal.
Let us clear the terminal. Type s is equal to inside quotes Hello World press Enter s inside square brackets minus five gives W Similarly we will get e for s[-10]. |
[Ipython Terminal]
Type s[-15] |
s inside square brackets minus 15 gives us an IndexError.
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[Ipython Terminal]
Type s[15] |
s inside square brackets 15 again gives IndexError for the same reason. |
[Ipython Terminal]
Press Up arrow till we get x Type x[0] = 'B' |
Let us attempt to change one of the characters in a string.
Let us clear the terminal. Recall x Press Enter Let us manipulate x. x inside square brackets zero equal to inside quotes B press Enter |
Highlight the error | Why do we get an error?
Initially the value of x[0] is ‘H’. Now we are trying to assign another value ‘B’ to x[0]. Recall, strings cannot be modified after it is created. |
Show slide split() and join() functions | We can split and join the strings by using the functions :
split() and join() |
Show slide
Syntax for join() str.join(sequence) |
To join a string, the syntax is
str dot join inside parentheses sequence |
[Ipython Terminal]
s = “-” seq = ("a", "b", "c") print (s.join( seq )) |
Switch to the terminal.
Let us clear the terminal Type s is equal to inside quotes hyphen press Enter seq is equal to inside parentheses a comma b comma c press Enter print s dot join inside parentheses seq press Enter |
Highlight a-b-c | We will get output as a hyphen b hyphen c
It has joined a, b, c with hyphen. |
Show slide syntax for split()
str.split() |
To split a string, syntax is
str dot split open and close parentheses |
[Ipython Terminal]
str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( )) |
Switch to the terminal
Type as shown press Enter
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Highlight ['Line1-abcdef', 'Line2-abc', 'Line4-abcd'] | We get the output like this.
It has split the strings at spaces. |
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Summary slide |
This brings us to the end of this tutorial.
In this tutorial, we have learnt to,
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Evaluation
s=Hello t=World r=2 What is the output of s * r + t * r? |
Here are some self assessment questions for you to solve
They are assigned with the values as shown below, What is the output of s multiplied by r plus t multiplied by r? |
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Solutions |
And the answers,
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Forum |
Please post your timed queries in this forum. |
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Fossee Forum |
Please post your general queries on Python in this forum. |
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Textbook Companion |
FOSSEE team coordinates the TBC project. |
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Acknowledgment |
Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.
For more details, visit this website. |
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Thank You |
This is Trupti Kini from IIT Bombay signing off.
Thank you. |