How to create a Python function which accepts multiple input arguments

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Published on - Listed in Coding Python


While I was working on a Python script, I wanted to create a function which should print additional (verbose) output for debugging purposes.

Python coding

TypeError: function() takes 1 positional argument but N were given

To do this, I created a function "verboseoutput" which is then called later in the script (while parsing JSON data):

[...]

# Verbose output for debugging help
def verboseoutput(message) :
    print(time.strftime("%Y%m%d %H:%M:%S"), message)



# handle json input
with open('tests/input.json', 'r') as json_file:
    data = json.load(json_file)

    for item in data:
        verboseoutput("Found elements:", item['Status'], item['Name'], item['Id'])

[...]

However when the Python script was executed, the following error message showed up:

ck@linux ~ $ python3 script.py
Traceback (most recent call last):
  File "/home/ck/script.py", line 93, in <module>
    verboseoutput("Found elements:", item['Status'], item['Name'], item['Id'])
TypeError: verboseoutput() takes 1 positional argument but 4 were given

The error hints that my verboseoutput() function only supports one (1) argument, but 4 were submitted to the function:

  1. "Found elements:" (string)
  2. item['Status'] (value from the parsed JSON data)
  3. item['Name'] (value from the parsed JSON data)
  4. item['Id'] (value from the parsed JSON data)

One solution would be to adjust the verboseoutput function and enter the exact amount of arguments:

# Verbose output for debugging help
def verboseoutput(arg1, arg2, arg3, arg4) :
    print(time.strftime("%Y%m%d %H:%M:%S"), message)

However this only works if the number of arguments always remain the same number.

Allow the function to accept variable number of arguments

As you can imagine, a verbose message could just be a single string - or could contain a list of variables. This function should therefore be flexible to accept anything it's been thrown at.

This can be done by setting the function to accept a variable number of arguments:

[...]

# Verbose output for debugging help
def verboseoutput(*message) :
    print(time.strftime("%Y%m%d %H:%M:%S"), message)

# handle json input
with open('tests/input.json', 'r') as json_file:
    data = json.load(json_file)

    for item in data:
        verboseoutput("Found elements:", item['Status'], item['Name'], item['Id'])

[...]

Noticed the asterisk in front of the input argument (*message)? This tells the function to accept a variable number of arguments as input.

After this change, the Python script is executed again and the verbose output is shown as expected:

ck@linux ~ $ python3 script.py
20240215 15:24:03 ('Found elements:', {'HealthRollup': 'OK', 'State': 'Enabled'}, 'HPE MR416i-o Gen11', 'DE00E000')
20240215 15:24:03 ('Found elements:', {'HealthRollup': 'OK', 'State': 'Enabled'}, 'HPE NS204i-u Gen11 Boot Controller', 'DE00B000')
20240215 15:24:03 ('Found elements:', {'HealthRollup': 'OK', 'State': 'Enabled'}, 'HPE NS204i-u Gen11 Boot Controller', 'DE00B000')



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