Does Python have an argc argument

Question

I have written the same program  open text file and display contents  in C and C    Now am doing the same in Python  on a Linux machine    In the C programs I used the code   if  argc    2           exit program        Question  What is used in Python to check the number of arguments     usr bin python import sys try      in file   open sys argv 1    r   except      sys exit  ERROR  Did you make a mistake in the spelling   text   in file read   print text in file close     Current output     python names txt   Displays text file  correct    python nam   error message  stated from the sys ext line  correct    python   error message  stated from the sys ext line  wrong  want it to be a separate error message stating  no file name input

User · Answer

I often use a quick-n-dirty trick to read a fixed number of arguments from the command-line:

[filename] = sys.argv[1:]

in_file = open(filename)   # Don't need the "r"

This will assign the one argument to filename and raise an exception if there isn't exactly one argument.

User · Answer

dir sys  says no  len sys argv  works  but in Python it is better to ask for forgiveness than permission  so      usr bin python import sys try      in file   open sys argv 1    r   except      sys exit  ERROR  Can t read supplied filename    text   in file read   print text  in file close     works fine and is shorter   If you re going to exit anyway  this would be better      usr bin python import sys text   open sys argv 1    r   read   print text    I m using print   so it works in 2 7 as well as Python 3

User · Answer

You re better off looking at argparse for argument parsing    http   docs python org dev library argparse html  Just makes it easy  no need to do the heavy lifting yourself

User · Answer

In python a list knows its length  so you can just do len sys argv  to get the number of elements in argv

[python] Does Python have an argc argument?

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