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Commit f665b67

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finish enumerate()
1 parent ffca067 commit f665b67

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3 files changed

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-0
lines changed

3 files changed

+344
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{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"# enumerate(iterable, start=0)\n",
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"\n",
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"`iterable` must be a sequence, an iterator, or some other object which **supports iteration**. The `__next__()` method of the iterator returned by `enumerate()` **returns a tuple containing a count (from start which defaults to 0) and the values obtained from iterating over iterable**."
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"If you've ever wanted to keep track of both index and value when manipulating a list,\n",
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"you probably did something like this:"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 7,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"The 0th fibonacci number is 1.\n",
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"The 1th fibonacci number is 1.\n",
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"The 2th fibonacci number is 2.\n",
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"The 3th fibonacci number is 3.\n",
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"The 4th fibonacci number is 5.\n",
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"The 5th fibonacci number is 8.\n",
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"The 6th fibonacci number is 13.\n",
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"The 7th fibonacci number is 21.\n"
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]
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}
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],
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"source": [
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"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
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"for i in range(len(fibonacci)):\n",
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" print(\"The {}th fibonacci number is {}.\".format(i, fibonacci[i]))"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"But if we wanted to start counting from 1 or something, we would need to do:"
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]
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},
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{
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"cell_type": "code",
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"execution_count": 8,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"The 1th fibonacci number is 1.\n",
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"The 2th fibonacci number is 1.\n",
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"The 3th fibonacci number is 2.\n",
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"The 4th fibonacci number is 3.\n",
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"The 5th fibonacci number is 5.\n",
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"The 6th fibonacci number is 8.\n",
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"The 7th fibonacci number is 13.\n",
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"The 8th fibonacci number is 21.\n"
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]
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}
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],
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"source": [
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"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
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"for i in range(len(fibonacci)):\n",
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" print(\"The {}th fibonacci number is {}.\".format(i+1, fibonacci[i]))"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"You can achieve the same results using the `enumerate()` function, but you instead get\n",
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"separate variables for your index and element, so it's a bit easier to read."
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]
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},
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{
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"cell_type": "code",
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"execution_count": 9,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"The 0th fibonacci number is 1.\n",
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"The 1th fibonacci number is 1.\n",
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"The 2th fibonacci number is 2.\n",
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"The 3th fibonacci number is 3.\n",
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"The 4th fibonacci number is 5.\n",
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"The 5th fibonacci number is 8.\n",
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"The 6th fibonacci number is 13.\n",
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"The 7th fibonacci number is 21.\n"
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]
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}
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],
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"source": [
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"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
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"\n",
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"for index, number in enumerate(fibonacci):\n",
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" print(\"The {}th fibonacci number is {}.\".format(index, number))"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
117+
"source": [
118+
"In more difficult problems, referring to `i+1`for counting, but using index `i`, could get confusing since \n",
119+
"they don't match. In this scenario, the `enumerate()` function gives us a little more flexibility since\n",
120+
"we can specify any `start` that we want:"
121+
]
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},
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{
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"cell_type": "code",
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"execution_count": 10,
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"metadata": {},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"The 1th fibonacci number is 1.\n",
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"The 2th fibonacci number is 1.\n",
134+
"The 3th fibonacci number is 2.\n",
135+
"The 4th fibonacci number is 3.\n",
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"The 5th fibonacci number is 5.\n",
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"The 6th fibonacci number is 8.\n",
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"The 7th fibonacci number is 13.\n",
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"The 8th fibonacci number is 21.\n"
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]
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}
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],
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"source": [
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"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
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"\n",
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"for index, number in enumerate(fibonacci, start=1):\n",
147+
" print(\"The {}th fibonacci number is {}.\".format(index, number))"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 3",
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"language": "python",
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"name": "python3"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython3",
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"version": "3.6.4"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 2
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}

‎built_in_functions/enumerate.ipynb

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{
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"cells": [
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{
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"cell_type": "markdown",
5+
"metadata": {},
6+
"source": [
7+
"# enumerate(iterable, start=0)\n",
8+
"\n",
9+
"`iterable` must be a sequence, an iterator, or some other object which **supports iteration**. The `__next__()` method of the iterator returned by `enumerate()` **returns a tuple containing a count (from start which defaults to 0) and the values obtained from iterating over iterable**."
10+
]
11+
},
12+
{
13+
"cell_type": "markdown",
14+
"metadata": {},
15+
"source": [
16+
"If you've ever wanted to keep track of both index and value when manipulating a list,\n",
17+
"you probably did something like this:"
18+
]
19+
},
20+
{
21+
"cell_type": "code",
22+
"execution_count": 7,
23+
"metadata": {},
24+
"outputs": [
25+
{
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"name": "stdout",
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"output_type": "stream",
28+
"text": [
29+
"The 0th fibonacci number is 1.\n",
30+
"The 1th fibonacci number is 1.\n",
31+
"The 2th fibonacci number is 2.\n",
32+
"The 3th fibonacci number is 3.\n",
33+
"The 4th fibonacci number is 5.\n",
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"The 5th fibonacci number is 8.\n",
35+
"The 6th fibonacci number is 13.\n",
36+
"The 7th fibonacci number is 21.\n"
37+
]
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}
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],
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"source": [
41+
"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
42+
"for i in range(len(fibonacci)):\n",
43+
" print(\"The {}th fibonacci number is {}.\".format(i, fibonacci[i]))"
44+
]
45+
},
46+
{
47+
"cell_type": "markdown",
48+
"metadata": {},
49+
"source": [
50+
"But if we wanted to start counting from 1 or something, we would need to do:"
51+
]
52+
},
53+
{
54+
"cell_type": "code",
55+
"execution_count": 8,
56+
"metadata": {},
57+
"outputs": [
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{
59+
"name": "stdout",
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"output_type": "stream",
61+
"text": [
62+
"The 1th fibonacci number is 1.\n",
63+
"The 2th fibonacci number is 1.\n",
64+
"The 3th fibonacci number is 2.\n",
65+
"The 4th fibonacci number is 3.\n",
66+
"The 5th fibonacci number is 5.\n",
67+
"The 6th fibonacci number is 8.\n",
68+
"The 7th fibonacci number is 13.\n",
69+
"The 8th fibonacci number is 21.\n"
70+
]
71+
}
72+
],
73+
"source": [
74+
"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
75+
"for i in range(len(fibonacci)):\n",
76+
" print(\"The {}th fibonacci number is {}.\".format(i+1, fibonacci[i]))"
77+
]
78+
},
79+
{
80+
"cell_type": "markdown",
81+
"metadata": {},
82+
"source": [
83+
"You can achieve the same results using the `enumerate()` function, but you instead get\n",
84+
"separate variables for your index and element, so it's a bit easier to read."
85+
]
86+
},
87+
{
88+
"cell_type": "code",
89+
"execution_count": 9,
90+
"metadata": {},
91+
"outputs": [
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{
93+
"name": "stdout",
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"output_type": "stream",
95+
"text": [
96+
"The 0th fibonacci number is 1.\n",
97+
"The 1th fibonacci number is 1.\n",
98+
"The 2th fibonacci number is 2.\n",
99+
"The 3th fibonacci number is 3.\n",
100+
"The 4th fibonacci number is 5.\n",
101+
"The 5th fibonacci number is 8.\n",
102+
"The 6th fibonacci number is 13.\n",
103+
"The 7th fibonacci number is 21.\n"
104+
]
105+
}
106+
],
107+
"source": [
108+
"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
109+
"\n",
110+
"for index, number in enumerate(fibonacci):\n",
111+
" print(\"The {}th fibonacci number is {}.\".format(index, number))"
112+
]
113+
},
114+
{
115+
"cell_type": "markdown",
116+
"metadata": {},
117+
"source": [
118+
"In more difficult problems, referring to `i+1`for counting, but using index `i`, could get confusing since \n",
119+
"they don't match. In this scenario, the `enumerate()` function gives us a little more flexibility since\n",
120+
"we can specify any `start` that we want:"
121+
]
122+
},
123+
{
124+
"cell_type": "code",
125+
"execution_count": 10,
126+
"metadata": {},
127+
"outputs": [
128+
{
129+
"name": "stdout",
130+
"output_type": "stream",
131+
"text": [
132+
"The 1th fibonacci number is 1.\n",
133+
"The 2th fibonacci number is 1.\n",
134+
"The 3th fibonacci number is 2.\n",
135+
"The 4th fibonacci number is 3.\n",
136+
"The 5th fibonacci number is 5.\n",
137+
"The 6th fibonacci number is 8.\n",
138+
"The 7th fibonacci number is 13.\n",
139+
"The 8th fibonacci number is 21.\n"
140+
]
141+
}
142+
],
143+
"source": [
144+
"fibonacci = [1, 1, 2, 3, 5, 8, 13, 21]\n",
145+
"\n",
146+
"for index, number in enumerate(fibonacci, start=1):\n",
147+
" print(\"The {}th fibonacci number is {}.\".format(index, number))"
148+
]
149+
}
150+
],
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"metadata": {
152+
"kernelspec": {
153+
"display_name": "Python 3",
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"language": "python",
155+
"name": "python3"
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},
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"language_info": {
158+
"codemirror_mode": {
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"name": "ipython",
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"version": 3
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},
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"file_extension": ".py",
163+
"mimetype": "text/x-python",
164+
"name": "python",
165+
"nbconvert_exporter": "python",
166+
"pygments_lexer": "ipython3",
167+
"version": "3.6.4"
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}
169+
},
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"nbformat": 4,
171+
"nbformat_minor": 2
172+
}

‎built_in_functions/enumerate.py

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