Python List within List - References

Question

I had a look through the other answers but couldn't really find an answer to mine.

The program needs to return a persons age given their name.

    recordslist = [["Daniel", 18], ["John", 19], ["Paul", 20], ["Jack", 44]]

         def(name):



    checkAge(str(input("What is your name?")))

For example if Daniel is entered, the program returns 18. If John is entered, the program returns 19.

I'm not sure how to code this. There must be a for and in command somewhere in that def.

Thanks :-)

you're using the wrong data type. Use a dict instead of a list of lists, like: records = {"Daniel":18, "John":19"} then do records[name] — Adam Smith
– Adam Smith, Commented Apr 15, 2014 at 2:14

shaktimaan · Accepted Answer · 2014-04-16 22:16:06Z

1

This is what you are looking for - dict(recordslist). A dictionary in Python is a key value pair. Your data can be better structured as a key value pair. Key being the name of the person and value being his/her corresponding score. dict(recordslist) converts your data from a list of lists to a dictionary.

You can access the value corresponding to a key in a dictionary as:

dictionary_variable[key]

Demo:

>>> recordslist = [["Daniel", 18], ["John", 19], ["Paul", 20], ["Jack", 44]]
>>> a_dict = dict(recordslist)
>>> a_dict
{'John': 19, 'Paul': 20, 'Daniel': 18, 'Jack': 44}
>>> a_dict['Daniel']
18

In your code you would do:

def checkAge(name, a_dict):
    if name in a_dict:
        return a_dict[name]
    else:
        return "No score found for {}".format(name)

result = checkAge(str(input("What is your name?")))
print result

Note: In order for this to work as you expect it to, you must have unique names in your list of list. This is what I mean:

>>> recordslist = [["Daniel", 18], ["John", 19], ["Paul", 20], ["Jack", 44], ["Daniel", 40]]
>>> a_dict = dict(recordslist)
>>> a_dict
{'John': 19, 'Paul': 20, 'Daniel': 40, 'Jack': 44}

I added ["Daniel", 40] to your recordslist and the a_dict has only one entry for Daniel.

edited Apr 16, 2014 at 22:16

answered Apr 15, 2014 at 2:13

shaktimaan

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7 Comments

Daniel Nitschke Over a year ago

Thanks, this answered things perfectly shak :-)

Daniel Nitschke Over a year ago

Hey Shak, I've just tried your code, and the program runs and asks for the name, but the program ends without displaying an age?

shaktimaan Over a year ago

@DanielNitschke Are you calling the function and with the right parameters?

shaktimaan Over a year ago

@DanielNitschke The function returns the result. Shouldn't you be either getting it's result in a variable and printing it OR printing the result in the checkAge method? Updated the answer to do so!

Daniel Nitschke Over a year ago

Heya, the old code should have just printed the return. I've adapted your new code, but am still receiving this parameter error: result = checkAge(str(input("What is your name?"))) TypeError: checkAge() missing 1 required positional argument: 'recordsdict'

|

Community · Accepted Answer · 2017-05-23 10:28:19Z

0

As shaktimaan suggested, a dict is the right data structure if you have unique names.

If you have multiple entries with the same name potentially, you can use a list comprehension:

>>> recordslist = [["Daniel", 18], ["John", 19], ["Paul", 20], ["Daniel", 22]]
>>> tgt="Daniel"
>>> [(name, age) for name, age in recordslist if name==tgt]
[('Daniel', 18), ('Daniel', 22)]

edited May 23, 2017 at 10:28

CommunityBot

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answered Apr 15, 2014 at 2:27

dawg

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