sys.argv
- Python course
- Beginner
- Lesson 98/116
- 4 min
Learn command-line arguments with sys.argv.
sys.argv
sys.argv is a list holding command-line arguments. It is used by importing the sys module:
import sys
print(sys.argv)
# python script.py Ayşe 25
# ["script.py", "Ayşe", "25"]sys.argv[0] is always the script name. Real arguments start at sys.argv[1]. Each argument is a string — convert if you need a number.
It is the way to read parameters given when the script starts.
argv and IndexError
If the user does not give enough arguments, accessing sys.argv[1] raises IndexError. So you must first check that the list has enough elements:
import sys
if len(sys.argv) > 1:
name = sys.argv[1]
else:
name = "misafir"
print(name)This pattern — first a length check, then access — prevents IndexError. Providing a default value makes the script robust.
This check is standard in command-line scripts.
Practice Greet with sys.argv
Write import sys. Assign sys.argv[1] if len(sys.argv) > 1 else "misafir" to name. Then write print("Merhaba, " + name). The script runs with no arguments.
Starter code
# bring in the sys module
# take argument if present, else use misafir
# print the greetingSample solution
import sys
name = sys.argv[1] if len(sys.argv) > 1 else "misafir"
print("Merhaba, " + name)Expected output
Merhaba, misafir
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Complete the sys.argv access
import sys
name = sys.____[1]import sys
name = sys.argv[1]Explanation: sys.argv[1] is the first real argument.
2 What does sys.argv[0] contain?
- An empty string
- The first argument
- The argument count
- The script name Correct answer
Explanation: sys.argv[0] is always the name of the script being run.
3 Match sys.argv concepts
| Term | Meaning |
|---|---|
sys.argv[0] |
Script name |
sys.argv[1] |
First argument |
len(sys.argv) |
Argument count |
import sys |
Required import |