max ( data, axis = 1 ) for val in values : print ( val ) main () A File-Checker mean ( data, axis = 1 ) elif action = '-max' : values = numpy. min ( data, axis = 1 ) elif action = '-mean' : values = numpy. loadtxt ( filename, delimiter = ',' ) if action = '-min' : values = numpy. stdin, action ) else : for filename in filenames : process ( filename, action ) def process ( filename, action ): data = numpy.
argv if len ( filenames ) = 0 : process ( sys. argv # start the filenames one place earlier in the argv listĮlse : filenames = sys. argv if action not in : # if no action givenĪction = '-mean' # set a default action, that being meanįilenames = sys. Import sys import numpy def main (): script = sys. Modify readings.py so that if no action is given max ( data, axis = 1 ) for val in values : print ( val ) main () Adding a Default Action 'Action is not one of -min, -mean, or -max: ' + action if len ( filenames ) = 0 : process ( sys. Otherwise, each filename in the list of arguments is processed in turn""" ) return action = sys. If filenames is blank, input is taken from stdin Print ( """Usage: python readings_08.py action filenames argv ) = 1 : # no arguments, so print help message The ‘1’ tells Python to start the slice at location 1, The solution to both problems is to loop over the contents of sys.argv. Since our program could be run for any number of files. We also need to handle an unknown number of filenames, Sys.argv will always be the name of our script, If we specify the files on the command line, So we need a loop that executes once for each filename. We want our program to process each file separately, Whereas we were really taking it on faith before. We can see that our program is calculating the mean correctly for each line, Using small data files as input also allows us to check our results more easily: We’ll start by using three smaller files,Įach of which has three days of data for two patients: Since 60 lines of output per file is a lot to page through,
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The next step is to teach our program how to handle multiple files. That is part of Python’s Official Documentation. We will not cover this module in this lesson Which handles common cases in a systematic way,Īnd also makes it easy for us to provide sensible error messages for our users. If our programs can take complex parameters or multiple filenames, In that script so that you can determine if the file
Script in bash, _name_ is always set to '_main_'
Of that file (e.g., when importing readings.py, When you import a Python file, _name_ is the name If _name_ = '_main_' : main () # Or whatever function produces output This program does exactly what we want - it prints the average inflammation per patient When you see a $ in front of aĬommand that tells you to run that command in the shell rather than the Python interpreter. In this lesson we are switching from typing commands in a Python interpreter to typingĬommands in a shell terminal window (such as bash). We may want a program that reads a datasetĪnd prints the average inflammation per patient. We need to make our programs work like other Unix command-line tools. Or run it in a shell script to process thousands of data files.
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The Jupyter Notebook and other interactive tools are great for prototyping code and exploring data,īut sooner or later we will want to use our program in a pipeline Read data from standard input in a program so that it can be used in a pipeline. Handle flags and files separately in a command-line program. Use the values of command-line arguments in a program.