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YWBAT
- loop through a dictionary and get specific items
- manipulate a string for a desired result
- use method chaining to manipulate a string
- method chaining - a function of an object's class
- ex:
my_string.replace('old', 'new')
- use the zip function to iterate over 2 lists
- use list comprehension to create a list
- list comprehension - building a list inline (within a single line of code)
p = True
if p:
x = 4
else:
x = 10
x4
x = 4 if p else 10 #inline conditional
x 4
import pandas as pd
import numpy as np
from collections import defaultdict
import matplotlib.pyplot as pltx = list(range(0, 21, 2))
# what is the expected result?
x[0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
# using a for loop, create a list (y)
# such that ever element in y is twice the element in x, respectively.
y = []
for i in x:
y.append(2*i)
y[0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40]
# using list comprehension, create a list (y)
# such that ever element in y is twice the element in x, respectively.
y = [2*i for i in x]
y [0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40]
lst1 = list(range(10))
lst2 = list('abcdefghijklmono')
# print(lst1)
# print(lst2)
# using the zip function, create a list lst3 that is a list of tuples
# lst3 = [(0, a), (1, b), ... , (9, j)]
# code here
# the old way of doing things
# it sucks but is super reliable
# commenting out for now
# lst3 = []
# for index in range(len(lst1)):
# tup = (lst1[index], lst2[index])
# lst3.append(tup)
# lst3
# let's use the zip function
# lst3 = list(zip(lst1, lst2))
lst3 = [(i, j) for i, j in zip(lst1, lst2)]
lst3[(0, 'a'),
(1, 'b'),
(2, 'c'),
(3, 'd'),
(4, 'e'),
(5, 'f'),
(6, 'g'),
(7, 'h'),
(8, 'i'),
(9, 'j')]
# now let's make the above lst3 into a dictionary
# d = {0: 'a', ..., 9: 'j'}
d = {}
for i, j in zip(lst1, lst2):
d[i] = j # assign value j to key i
d{0: 'a',
1: 'b',
2: 'c',
3: 'd',
4: 'e',
5: 'f',
6: 'g',
7: 'h',
8: 'i',
9: 'j'}
# shortcut time
d = dict(zip(lst1, lst2))
d{0: 'a',
1: 'b',
2: 'c',
3: 'd',
4: 'e',
5: 'f',
6: 'g',
7: 'h',
8: 'i',
9: 'j'}
# let's spell out 'cab'
my_word = d[2] + d[0] + d[1]
my_word'cab'
d.get(12, d[len(d) - 1]) 'j'
# default dict
numbers = list(range(30))
print(numbers)[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29]
# make a dictionary with
# d['evens'] = [0, 2 , 4, ..., 28]
# d['odds'] = [1, 3, ..., 29]
d = defaultdict(list)
for number in numbers:
if number%2==0:
d['evens'].append(number)
else:
d['odds'].append(number)
ddefaultdict(list,
{'evens': [0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28],
'odds': [1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29]})
list(zip(lst1, lst2, lst3))[(0, 'a', (0, 'a')),
(1, 'b', (1, 'b')),
(2, 'c', (2, 'c')),
(3, 'd', (3, 'd')),
(4, 'e', (4, 'e')),
(5, 'f', (5, 'f')),
(6, 'g', (6, 'g')),
(7, 'h', (7, 'h')),
(8, 'i', (8, 'i')),
(9, 'j', (9, 'j'))]
- learned that
zipcreates tuples from multiple lists - inline coding, specifically how to create conditions (if statements) inline
- inline coding, for loops
- list comprehension : creating a list from a single line of code
getmethod on dictionaries returns values of keys or a default value
lst2.index('d')3
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