ListsCreate an empty list | newlist=[] | Assign value at index | alist[index]= value | Access value at index | alist[index] | Add item to list | alist.append(new item) | Insert into list | alist.insert(at position, new item) | Count # of an item in list | alist.count( item ) | Delete 1 matching item | alist.remove(del item) | Remove item at index | del alist[index] |
LoopingFor loop 0 thru 9 | for x in range(10): | For loop 5 thru 10 | for x in range(5,11): | For each char in a string | for char in astring: | For items in list | for x in alist: | For indexes/values in a list | for index,value in enumerate(alist): | For each key in a dict | for x in adict.keys(): | For all items in dict | for key,value in adict.items(): | while <logic test> | do: | Exit loop immediately | break | Skip rest of loop and do loop again | continue |
Logic and Math OperatorsMath Operator | Example | X=7, Y=5 | Addition | X + Y | 12 | Subtraction | X - Y | 2 | Multiplication | X * Y | 35 | Division | X / Y | 1.4 | Floor | X // Y | 1 | Exponent | X ** Y | 16807 | Modulo | X % Y | 2 | Logic Operator | Equality | X == Y | False | Greater Than | X > Y | False | Less Than | X < Y | True | Less or Equal | X <= Y | True | Not Equal | X !=Y or X<>Y | True | Bitwise Exclusive Or | a ^ b xor(a, b) |
Converting Data TypesCovert | Syntax | Example | Result | Num -> string | str(number) int, float or long | str(100) str(3.14) | '100' '3.14' | Encoded bytes -> string | str(txt,encoding) | str(data,"utf8") | string with data | Num String -> int | int("string",base) default base is 10 | int("42") int("101",2) int("ff", 16) | 42 5 255 | int -> hex string | hex(integer) | hex(255) hex(10) | '0xff' '0xa' | integer -> binary string | bin(integer) | bin(5) bin(3) | '0b101' '0b11' | float -> integer | int(float) drops decimal | int(3.14159) int(3.9) | 3 3 | int or str -> float | float(int or str) | float("3.4") float(3) | 3.4 3.0 | String -> ASCII | ord(str) | ord("A") ord("1") | 65 49 | int -> ASCII | chr(integer) | chr(65) chr(49) | 'A' '1' | bytes -> string | <bytes>.decode() | b'ABC'.decode() | 'ABC' | string -> bytes | <str>.encode() | 'abc'.encode() | b'abc' |
Useful OS functionsimport os | Executing a shell command | os.system() | Rename the file or directory src to dst | os.rename(src, dst) | Change working directory | os.chdir(path) | Get the users environment | os.environ() | Returns the current working directory | os.getcwd() |
| | DictionariesCreate an empty dict | dict={} | Initialize a non-empty dictionary | dict= { “key”:”value”,”key2”:”value2”} | Assign a value | dict[“key”]=”value” | Determine if key exists | "key" in dict | Access value at key | dict[“key”], dict.get(“key”) | Iterable View of all keys | dict.keys() | Iterable View of all values | dict.values() | Iterable View of (key,value) tuples | dict.items() |
Slicing and Indexingx[start:stop:step] | x=[4,8,9,3,0] | x=”48930” | x[0] | 4 | ‘4’ | x[2] | 9 | '9' | x[:3] | [4,8,9] | '489' | x[3:] | [3,0] | '30' | x[:-2] | [4,8,9] | '489' | x[::2] | [4,9,0] | ‘490’ | x[::-1] | [0,3,9,8,4] | ‘03984’ | len(x) | 5 | 5 | sorted(x) | [0,3,4,8,9] | ['0','3','4','8','9'] |
MiscAdding Comments to code:
#Comments begin the line with a pound sign
Adding Multi-line Comment to code
"""
Multi-Line Comment
"""
Get user input from keyboard
name = input("What is your name? ")
Functions
def add(num1, num2):
#code blocks must be indented
#each space has meaning in python
myresult = num1 + num2
return myresult
if then else statements
if <logic test 1>:
#code block here will execute
#when logic test 1 is True
elif <logic test 2>:
#code block executes if logic test 1 is
#False and logic test 2 is True
else:
#else has no test and executes when if
#and all elif are False
python3 shebang
#!/usr/bin/env python3
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PrintingStandard print | print('{}'.format(STRING)) | Print string variable | print ("I am %s" % name) | Print int variable | print ("I am %d" % number) | Print with + | print ("I am " + name) |
String OperationsMake lowercase | "Ab".lower()="ab" | Make UPPERCASE | "Ab".upper()="AB" | Make Title Format | "hi world".title()="Hi World" | Replace a substring | "123".replace('2','z')= "1z3" | Count occurrences of substring | "1123".count("1")=2 | Get offset of substring in string | "123".index("2")=1 | Detect substring in string | “is” in “fish” == True |
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