Python 10b - Read & Search Files
Reading from a File
To read and print from a file you must open it in read mode by typing "r" instead of "a".
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If you are writing and reading in the same program, make sure you close the file in append mode before you open it in read mode.
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The program below uses the Customers.txt file from the last section.
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A simple for loop can be used to print each line of the file.
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The end = "" code just prevents a space between each line.
Practice Task 1
Open one of the files that you used in Section 10a and print each line.
Example solution:
Reading Specific Lines from a File
Sometimes it is necessary only to print certain lines.
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The following example uses a file where I have written a sentence of advice on each line.
The user is asked to enter a number between 1 and 6.
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If they enter 1, the first line of the file is printed. If they enter 2, the second line of the file is printed etc.
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Remember Python starts counting everything at 0 so each line is a digit less than you would expect.
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Square brackets must be used to denote the line to print: [1] not (1).
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The end = "" code is not necessary but removes space after the line.
Practice Task 2
Create a text file (saved in the same folder as your Python file) with a list of video games.
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Ask the user to enter a number between 1 and 10.
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Print the line for the number that they input.
Example solution:
Searching Through Files
A for loop is used to search through a file, line by line.
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First, an input line is used to allow the user to enter their search term.
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If the term that is being searched for is found, then the whole line is printed.
The example below uses a variable named found to state if there is a match when the file is searched.
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If the search term is found, then the found variable is changed to true.
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If the search term is not found, the found variable remains as false, so the 'no customers found' statement is printed.
Practice Task 3
You should have completed Practice Task 2 from Section 10a (the A Level task).
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Add extra code to that program so that you can search for specific students.
Example solution:
