Python 3 Flashcards
How to comment in Python?
#
How to print in Python?
print(text here)
Float number
Number with a decimal
How to do exponents?
**
Example: For 62, you would write 6**2
How to make a multiline string?
””” or ‘’’
How to assign a variable to user input?
input(text here)
Boolean operators in Python
and, or, not
Else if statement
elif
Syntax Error
Error caused by not following the proper syntax of the language
Name Error
Error caused when an unknown variable is used
Type Error
Error caused when you do an operation on an incorrect type
how to concatanate Strings with ints or doubles
use a comma instead of a plus sign
How to create a list
variable = [stuff here, separated by commas]
True or False: Lists can contain any data type
True
How to add something to the end of a list?
list.append(“”)
list concatination
use the + symbol and store it in a new list
How to access the last element of a list
use -1 (-2 would access second to last, etc.)
How to add an element to a specific index in a list?
.insert(index, element)
How to remove an element by index
.pop(index)
you can also do .pop() with no parameters and it will remove the last index
what does range() do
range(10)
will create a range object with numbers 0 -> 9
range(2, 9)
will create a range object with numbers 2 -> 8
range(2, 9, 2)
will create a range object where each number is 2 greater than the previous
[2, 4, 6, 8]
note: because it is a range object, you need to convert it into a list using list(my_range)
how to find the number of items in a list
len(my_list)
how to slice a list
list_name[first index:last index]
note: it goes up to but not including last index
what does list[:n] do?
selects the first n objects in a list (also works for negative, list[-n:] will select that last n objects in a list
.count() method
will count the amount of times the parameter appears in a list (can also be used with 2d lists)
.sort() method
will sort a list by numerical or alphabetical orders
how to sort a list in reverse order
.sort(reverse=True)
what is a tuple?
a data structure in python that allows us to store multiple pieces of data inside of it. similar to a list except that it is inmutable
how to make a tuple
use () instead of []
unpacking a tuple
you can use a tuple to set lots of variables with one line
example:
my_info = (‘mike’, 24, ‘programmer’
name, age, occupation = my_info
it will create three different variables, each assigned to the relative index of the tuple
how to create a one element tuple
you MUST include a comma, or else it is just a regular data type
example:
WRONG -> one_element_tuple = (4)
RIGHT -> one_element_tuple = (4,)
how to use the zip() function
- use it to combine 1D lists into 2D lists
names_and_heights = zip(names, heights)
note: will create a zip object, need to cast as a list using list(names_and_heights) to print - also, inner lists will become tuples
for loop strucure
for <temporary> in <list></list></temporary>
<action>
</action>
elegant for loop
for ingredient in ingredients: print(ingredient)
(a one line loop)
how to use range in for loops
Allows you to perform an action multiple times
(like loops in java)
for temp in range(6)
continue statement
will stop the current iteration of the loop, move on to the next one
list comprehensions
new_list = [<expression> for <element> in <collection>]
example: (will double each number in numbers)
numbers = [2, -1, 79, 33, -45]
doubled = [num * 2 for num in numbers]
print(doubled)</collection></element></expression>
function definition
def function_name():
Keyword Arguments
explicitly refer to what each argument is assigned to in the function call. example:
calculate_taxi_price(rate=0.5, discount=10, miles_to_travel=100)
Positional Arguments
arguments that can be called by their position in the function definition
Default argument
When a default value is provided. You can either choose to call the function without the value for the default (and the function will use the default value) or you can provide the value.
example:
def calculate_taxi_price(miles_to_travel, rate, discount = 10):
max() & min() function
will get the maximum or minimum of all the parameters in it
round() function
will round parameter to either:
- integer if only one parameter is used
- whichever decimal place you want to round it to if two parameters are use
example:
(to round 9.75 to one decimal place)
round(9.75, 1)
multiple returns
you can return multiple things
example:
return first_day, second_day, third_day
then you assign it to three variable like this:
monday, tuesday, wednesday = threeday_weather_report(weather_data)
print(monday)
print(tuesday)
print(wednesday)
