On this page we'll keep track of the Python types, functions, and operators that we've covered in class. You can also review the online Python References for more complete coverage, BUT NOTE there is far more detail on the Python documenation than we will cover!

The reference page below is all you should need to complete the exam.

Mathematical Operators | ||
---|---|---|

Symbol | Meaning | Example |

+ | addition | 4 + 5 = 9 |

- | subtraction | 9 - 5 = 4 |

* | multiplication | 3*5 = 15 |

/ | division | 6/4 = 1.5 |

// | floor division | 6//4 = 1 |

% | mod/remainder | 5 % 3 = 2 |

** | exponentiation | 3**2 = 9, 2**3 = 8 |

String Operators | ||

+ | concatenation | "ab"+"cd"="abcd" |

* | repeat | "xo"*3 = "xoxoxo" |

Comparison Operators | ||

== | is equal to | 3 == 3 is True |

!= | is not equal to | 3 != 3 is False |

>= | is greater than or equal to | 4 >= 3 is True |

<= | is less than or equal to | 4 <= 3 is False |

> | is strictly greater than | 4 > 3 is True |

< | is strictly less than | 3 < 3 is False |

Boolean Operators | ||

`x=5` | ||

not | flips/negates the value of a bool | (not x == 5) is False |

and | returns True only if both parts of it are True | (x > 3 and x < 7) is True (x > 3 and x > 7) is False |

or | returns True if at least one part of it is True | (x < 3 or x > 7) is False (x < 3 or x < 7) is True |

Type Conversion Functions | ||

int(x) | turn x into an integer value | int("123") == 123 |

int can fail, e.g., int("abc") raises an error | ||

float(x) | turn x into an float value | float("2.46") == 2.46 |

float can fail, e.g., float("abc") raises an error | ||

str(x) | turn x into a string value | str(432) == "432" |

type(x) | the type of x | type(1) ==
int type(1.2) == float |

String Functions | ||

`s="colorful"` | ||

Name | Returns | Example |

.find(str) | index of first occurrence | s.find("o") == 1 |

s.find("e") == -1 | ||

.rfind(str) | index of last occurrence | s.rfind("o") == 3 |

s.rfind("e") == -1 | ||

.count(str) | number of occurrences | s.count("o") == 2 s.count("r") == 1 s.count("e") == 0 |

.strip() | copy with leading/trailing whitespace removed | " big ".strip() == "big" |

.split() | list of "words" in s separated by whitespace | "big bad dog".split() == ["big","bad", "dog"] |

.split(",") | list of "items " in s that are separated
by a comma
In general can split on any string, not just a comma,
e.g., s.split(":") will split on a colon and
s.split("gat") will split on the string "gat". | "this,old,man".split(",") == ["this", "old", "man"] |

' '.join(lst) | concatenate elements of lst, a list of strings, separated by ' ' or any string | ':'.join(['a','b','c']) == "a:b:c" |

.startswith(str) | boolean if starts with string | s.startswith("color") == True s.startswith("cool") == False |

.endswith(str) | boolean if ends with string | s.endswith("ful") == True s.endswith("color") == False |

.upper() | uppercase of s | s.upper() == "COLORFUL" |

.lower() | lowercase of s | "HELLO".lower() == "hello" |

Miscellaneous Functions | ||

len(x) | length of sequence x, e.g., String/List | len("duke") == 4 |

list(str) | a list of the characters from string str | list("cards") == ['c','a','r','d','s'] |

sorted(x) | return list that is sorted version of sequence/iterable x, doesn't change x | sorted("cat") == ['a','c','t'] |

range(x) | a sequence of integers starting at 0 and going up to but not including x | range(5) == [0, 1, 2, 3, 4] |

range(start, stop) | a sequence of integers starting at start and going up to but not including stop | range(3, 7) == [3, 4, 5, 6] |

range(start, stop, inc) | a sequence of integers starting at start and going up to but not including stop with increment inc | range(3, 9, 2) == [3, 5, 7] |

min(x, y, z) | minimum value of all arguments | min(3, 1, 2) == 1
min("z", "b", "a") == "a" |

max(x, y, z) | maximum value of all arguments | max(3, 1, 2) == 3
max("z", "b", "a") == "z" |

abs(x) | absolute value of the int or float x | abs(-33) == 33 abs(-33.5) == 33.5 |

List Functions | ||

sum(lst) | returns sum of elements in list lst
| sum([1,2,4]) == 7 |

max(lst) |
returns maximal element in lst
| max([5,3,1,7,2]) == 7 |

lst.append(...) | append an element to lst, changing lst | [1,2,3].append(8) == [1,2,3,8] |

lst.count(elt) | return number of occurrences of elt in `lst`
| [1,2,1,2,3].count(1) == 2 |

Math Functions (import math) | ||

math.pi | 3.1415926535897931 | |

math.sqrt(num) | returns square root of num as float | math.sqrt(9) == 3.0 |

File Functions | ||

open("filename") | opens a file, returns file object | f = open("foo.txt") |

f.readlines() | returns the entire file as a list of lines (strings) | s = f.readlines() |

f.close() | close the file f | |

Random Functions (import random) | ||

random.randint(start, end) | Returns a random integer between start and end. Unlike range() and list slicing, the largest value it can return is end, not end-1. | |

random.random() | Returns a random float between 0 and 1. |