Typesstr  'abcd'  int  1,2,3,4  float  1.23  bool  True/False  None  None  type('abc')  shows the type of the object  type conversion  int('123') > 123  bool(x)  False for x values that are null or empty x. True for otherwise  Naming conventions  lowercase and underscore (_HAPPYday, happyday) 
Order of growthdef factorial(n): if n < 2: return 1 return n * factorial(n  1)  O(n)  def fib(n): if n < 2: return 1 return fib(n  1) + fib(n  2)  O(2^n) (each branch produces another 2 branches)  def foo(n): while n > 1: print(n) n = n // 2  O(log n)  def bar(n): while n > 1: x = n while x > 1: print(n, x) x = 1 n = 1  O(n^2) (loop in a loop)  def baz(n): while n > 1: x = n while x > 1: print(n, x) x = x // 2 n = 1  O(n log n) (log n in a loop)  String and tuple slicing  Slicing is an O(n) operation as you need to create another string/tuple when you slice.  def count_me(n): if n < 10: return n else: return count_me(n + 1)  O(infinity)  String and tuple concatenation  O(n) 
Time complexity> looking at the branches of the tree
Space complexity> looking at the depth of the tree (depends on the pending operations the function incurred)
And also for analysing OOG questions:
for <loop>:
<do work>
Time
= work(1) + work(2)+...+work(n)
If work is fixed (let's say work = k) regardless of n, Time = n * k
Otherwise,
Time = sum of work
Remember to state what the n means
Recursive and IterationRecursion
def recusive_fn(n):
if <base case>:
return <base case value>
else:
return <manipulate recursive_fn(n1) such that it becomes nth case>
Iteration (for or while loop)
def iterative_fn(n):
temp = <some basic value>
for i in <range>:
<update temp>
return temp
def factorial (n):
product , counter = 1,1
while counter <= n:
product *= counter
counter += 1
return product

Tuples comparisonTuples are compared position by position: the first item of the first tuple is compared to the first item of the second tuple (same as string); if they are not equal (i.e. the first is greater or smaller than the second) then that's the result of the comparison, else the second item is considered, then the third and so on.

  Truth values revisitedTruth and False will be represented by 1 and 0 respectively.
not 'abc' > False
1 or 0 > 0
'' is same as False is same as 0 is same as []
while True: infinite looping
while False: will not loop at all

String and tuple slicings[start:stop(noninclusive):step]
eg) s = "12345", d ='6789'
concatenate> s + d> '123456789'
s[0] = "1", s[1:]= "2345", s[:2]= "12", s[1:5:2] = "13"
s[1] = "5", s[1:3] = "", s[3:1]= '34', s[5:1:2]= '13', s[5:1:2]= ''', s[1:5:2] = '53'

Variable (Global and Local)Variable is local if assigned to in function
Namespaces match function and variable names to their definitions and assignments
Random modulerandom.randint(a, b)  Return a random integer N such that a <= N <= b.  random.randrange(start, stop[, step])  Return a randomly selected element from range(start, stop, step). This is equivalent to choice(range(start, stop, step)), but doesn’t actually build a range object  random.random()  Return the next random floating point number in the range [0.0, 1.0).  random.random() can be scaled  int(random.random() * 9999) → 3658 
breakfor val in "string":
if val == "i":
break
print(val)
print("The end")
Output:
s
t
r
The end

The break statement terminates the loop containing it. Control of the program flows to the statement immediately after the body of the loop.
If break statement is inside a nested loop (loop inside another loop), break will terminate the innermost loop.
Hiding 'something'Input an empty (lambda : "Prof is really cool")
In that way what is printed or sliced/accessed will be the function itself.
To recover the secret message, can input () at the back.

  Functionsdef <name>(formal parameters):
body
return (something if not it is going to return to zero)
Anonymous function→ lambda
lambda x: x+ 1
A function need not use every parameter passed into it. (def foo(a, b): return a + a)
A function without any parameters or return value is still valid. (def foo():return )
Functions do not necessarily need a return value.(def foo(a, b, c):a + b + c)

Conditionalsif <statement>:
do something
elif <statement>:
do something
else <statement>:
do something
while <statement>:
do something

Equality/ in functionis  This means the same object. (3 is 3)> True  ==  This mean the same content. (3.00 == 3) > True  in  check the elements inside the other group. Eg) x = (1,2,3). 1 in x> True 
Different Types of ErrorNameError  Raised when a variable is not found in local or global scope.  IndexError  Raised when index of a sequence is out of range.  RuntimeError  Raised when an error does not fall under any other category.  SyntaxError  Raised by parser when syntax error is encountered  ZeroDivisionError  Raised when second operand of division or modulo operation is zero.  UnboundLocalError  Raised when a reference is made to a local variable in a function or method, but no value has been bound to that variable  RecursionError  Infinite looping 
Tuple and string functionslen()  Return the length (the number of items) in the tuple.  max()  Return the largest item in the tuple.  min()  Return the smallest item in the tuple  sum()  Retrun the sum of all elements in the tuple.  tuple()  Convert an iterable (list, string, set, dictionary) to a tuple.  count()  count the occurrences of an element in a tuple  index()  Searches the string for a specified value and returns the position of where it was found 
continuefor val in "string":
if val == "i":
continue
print(val)
print("The end")
Output:
s
t
r
n
g
The end

The continue statement is used to skip the rest of the code inside a loop for the current iteration only. Loop does not terminate but continues on with the next iteration.

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