Assigning and Calling built-in functions from a dictionary (Python)

user_15140716 0
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everyone. I am trying to solve a coding challenge as follows:

  1. get a string from the user. Afterward, ask the user "What would you like to do to the string?", allow the user to choose the next functionalities: "upper" - makes all the string upper case "lower" - makes all the string lower case " "spaces2newline" - reaplce all spaces in new lines ... print the result *Use a dictionary to "wrap" that menu

So, what I am getting from this is that I need to make a dictionary from which I can call commands and assign them to the string.

Obviously, this doesn't work:

commands = {"1" : .upper(), "2" : .lower(), "3" : .replace(" ",\n)}

user_string = input("Enter a string: ")
options = input("How would you like to alter your string? (Choose one of the following:)\n
\t1. Make all characters capital\n
\t2. Make all characters lowercase")
#other options as input 3, 4, etc...

But perhaps someone can recommend a way to make the idea work?

My main questions are:

  1. Can you somehow assign built-in functions to a variable, list, or dictionary?
  2. How would you call a function like these from a dictionary and add them as a command to the end of a string?

Thanks for any assisstance!

built-in dictionary python
3 Answers

Use operator.methodcaller.

from operator import methodcaller


commands = {"1": methodcaller('upper'),
            "2": methodcaller('lower'),
            "3": methodcaller('replace', " ", "\n")}

user_string = input("Enter a string: ")
option = input("How would you like to alter your string? (Choose one of the following:)\
\t1. Make all characters capital\
\t2. Make all characters lowercase")

result = commands[option](user_string)

The documentation shows a pure Python implementation, but using methodcaller is slightly more efficient.

user_11268410

Well, chepner's answer is definitely much better, but one way you could have solved this is by directly accessing the String class's methods like so:

commands = {"1" : str.upper, "2" : str.lower, "3" : lambda string: str.replace(string, " ", "\n")}  # use a lambda here to pass extra parameters

user_string = input("Enter a string: ")
option = input("How would you like to alter your string? (Choose one of the following:)\
\t1. Make all characters capital\
\t2. Make all characters lowercase")

new_string = commands[option](user_string)

By doing this, you're saving the actual methods themselves to the dictionary (by excluding the parenthesis), and thus can call them from elsewhere.

user_130109560

maybe you could do:

command = lambda a:{"1" : a.upper(), "2" : a.lower(), "3" : a.replace(" ",'\n')}

user_string = input("Enter a string: ")
options = input("How would you like to alter your string? (Choose one of the following:)")
print("output:",command(user_string)[options])
#\t1. Make all characters capital\n
user_132857070
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