class Python Data Science Toolbox

map函数的使用：

• In the map() call, pass a lambda function that concatenates the string '!!!' to a string item; also pass the list of strings, spells. Assign the resulting map object to shout_spells.
• Convert shout_spells to a list and print out the list.

# Create a list of strings: spells
spells = ["protego", "accio", "expecto patronum", "legilimens"]


# Use map() to apply a lambda function over spells: shout_spells
shout_spells = map(lambda item : item + "!!!", spells)


# Convert shout_spells to a list: shout_spells_list
shout_spells_list = list(shout_spells)


# Convert shout_spells into a list and print it
print(shout_spells_list)

filter 函数的使用：

• In the filter() call, pass a lambda function and the list of strings, fellowship. The lambda function should check if the number of characters in a string member is greater than 6; use the len() function to do this. Assign the resulting filter object to result.
• Convert result to a list and print out the list.

# Create a list of strings: fellowship
fellowship = ['frodo', 'samwise', 'merry', 'aragorn', 'legolas', 'boromir', 'gimli']


# Use filter() to apply a lambda function over fellowship: result
result = filter(lambda member : len(member) > 6, fellowship)


# Convert result to a list: result_list
result_list = list(result)


# Convert result into a list and print it
print(result_list)

reduce函数的使用：

# Define gibberish
def gibberish(*args):
    """Concatenate strings in *args together."""
    hodgepodge = ''
    for word in args:
        hodgepodge += word
    return hodgepodge

gibberish() simply takes a list of strings as an argument and returns, as a single-value result, the concatenation of all of these strings. In this exercise, you will replicate this functionality by using reduce() and a lambda function that concatenates strings together.

Instructions

• Import the reduce function from the functools module.
• In the reduce() call, pass a lambda function that takes two string arguments item1 and item2 and concatenates them; also pass the list of strings, stark. Assign the result to result. The first argument to reduce() should be the lambda function and the second argument is the list stark.

# Import reduce from functools
from functools import reduce


# Create a list of strings: stark
stark = ['robb', 'sansa', 'arya', 'eddard', 'jon']


# Use reduce() to apply a lambda function over stark: result
result = reduce(lambda item1,item2 : item1 + item2, stark)


# Print the result
print(result)