DS4UX (Spring 2016)/Day 3 follow up: Difference between revisions
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Here are some important concepts that we didn't have a chance to go into in great detail last week. You can use the sections below to review the concepts individually. You can also review how they work together in <code>math_game.py</code>. | |||
* | ===Select random items from a set with <code>random.choice()</code>=== | ||
* | |||
*. | |||
===Generating a list of numbers easily with <code>range()</code>=== | |||
<pre> | |||
>>> range(5) | |||
[0, 1, 2, 3, 4] | |||
>>> for i in range(5): | |||
... print("Hi" * i) | |||
... | |||
Hi | |||
HiHi | |||
HiHiHi | |||
HiHiHiHi</pre> | |||
The <code>range()</code> function returns a list of numbers. This is handy for when you want to generate a list of numbers on the fly instead of creating the list yourself. | |||
>>> range(5) | |||
[0, 1, 2, 3, 4] | |||
Use <code>range</code> when you want to loop over a bunch of numbers in a list, or perform an operation a certain number of times: | |||
>>> numbers = range(5) | |||
>>> for number in numbers: | |||
... print(number * number) | |||
... | |||
0 | |||
1 | |||
4 | |||
9 | |||
16 | |||
We could rewrite the above example like this: | |||
>>> for number in range(5): | |||
... print(number * number) | |||
... | |||
0 | |||
1 | |||
4 | |||
9 | |||
16 | |||
You can also set the start, end, and increment value (called "step") for a range. | |||
>>> for i in range(2,20,2): | |||
... print(i) | |||
2 | |||
4 | |||
6 | |||
8 | |||
10 | |||
12 | |||
14 | |||
16 | |||
18 | |||
=== Get user input with <code>input()</code> === | |||
>>> for i in range(100): | |||
... my_input = input("Please type something> ") | |||
... if my_input == "Quit": | |||
... print("Goodbye!") | |||
... break | |||
... else: | |||
... print("You said: " + my_input) | |||
... | |||
Please type something> Hello | |||
You said: Hello | |||
Please type something> How are you? | |||
You said: How are you? | |||
Please type something> Quit | |||
Goodbye! | |||
>>> | |||
=== Iterating an indeterminate number of times with <code>while</code> loops === | |||
grocery_list = [] | |||
testAnswer = input('Press y if you want to enter more groceries: ') | |||
while testAnswer == 'y': | |||
food = input('Next item:') | |||
grocery_list.append(food) | |||
testAnswer = input('Press y if you want to enter more groceries: ') | |||
print('Your grocery list:') | |||
for food in grocery_list: | |||
print(food) | |||
===Splicing list items together with <code>.join</code=== |
Revision as of 22:46, 17 April 2016
Here are some important concepts that we didn't have a chance to go into in great detail last week. You can use the sections below to review the concepts individually. You can also review how they work together in math_game.py
.
Select random items from a set with random.choice()
Generating a list of numbers easily with range()
>>> range(5) [0, 1, 2, 3, 4] >>> for i in range(5): ... print("Hi" * i) ... Hi HiHi HiHiHi HiHiHiHi
The range()
function returns a list of numbers. This is handy for when you want to generate a list of numbers on the fly instead of creating the list yourself.
>>> range(5) [0, 1, 2, 3, 4]
Use range
when you want to loop over a bunch of numbers in a list, or perform an operation a certain number of times:
>>> numbers = range(5) >>> for number in numbers: ... print(number * number) ... 0 1 4 9 16
We could rewrite the above example like this:
>>> for number in range(5): ... print(number * number) ... 0 1 4 9 16
You can also set the start, end, and increment value (called "step") for a range.
>>> for i in range(2,20,2): ... print(i) 2 4 6 8 10 12 14 16 18
Get user input with input()
>>> for i in range(100): ... my_input = input("Please type something> ") ... if my_input == "Quit": ... print("Goodbye!") ... break ... else: ... print("You said: " + my_input) ... Please type something> Hello You said: Hello Please type something> How are you? You said: How are you? Please type something> Quit Goodbye! >>>
Iterating an indeterminate number of times with while
loops
grocery_list = [] testAnswer = input('Press y if you want to enter more groceries: ') while testAnswer == 'y': food = input('Next item:') grocery_list.append(food) testAnswer = input('Press y if you want to enter more groceries: ')
print('Your grocery list:') for food in grocery_list: print(food)