Python笔记 #03# Help!

源：DataCamp

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Functions

Built-in functions

Help!

Multiple arguments

Functions

By now, you have an idea about how to use max() and round(), but how could you know that a function such as round() exists in Python in the first place? Well, this is something you will learn with time. Whenever you are doing a rather standard task in Python, you can be pretty sure that thers is already a function that can do this for you. In that case, you should definitely use it! Just do a quick internet search and you will find the function you need with a nice usage example!

Built-in functions

# Create variables var1 and var2
var1 = [1, 2, 3, 4]
var2 = True

# Print out type of var1
print(type(var1))

# Print out length of var1
print(len(var1))

# Convert var2 to an integer: out2
out2 = int(var2)

Help!

Maybe you already know the name of a Python function, but you still have to figure out how to use it. Ironically, you have to ask for information about a function with another function: help().

To get help on the max() function, for example, you can use one of these calls:

help(max)
?max

Use the Shell on the right to open up the documentation on complex(). Which of the following statements is true?

Multiple arguments

Have a look at the documentation of sorted() by typing help(sorted) in the IPython Shell.

You'll see that sorted() takes three arguments: iterable, key and reverse.

key=None means that if you don't specify the keyargument, it will be None. reverse=False means that if you don't specify the reverse argument, it will be False.

In this exercise, you'll only have to specify iterable and reverse, not key. The first input you pass to sorted()will be matched to the iterable argument, but what about the second input? To tell Python you want to specify reverse without changing anything about key, you can use =:

sorted(___, reverse = ___)

# Create lists first and second
first = [11.25, 18.0, 20.0]
second = [10.75, 9.50]

# Paste together first and second: full
full = first + second

# Sort full in descending order: full_sorted
full_sorted = sorted(full, reverse=True)

# Print out full_sorted
print(full_sorted)