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Python Coding Interview Cheat Sheet (DRAFT) by

Python Coding Interview

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Type built-in

bool(x=False)
bytearray(source=b'')
bytearray(source, encoding, errors)
bytes(source=b'')
bytes(source, encoding, errors)
complex(real=0, imag=0)
complex(string)
dict(**kwarg)
dict(mapping, **kwarg)
dict(iterable, **kwarg)
float(x=0.0)
int(x=0)
int(x, base=10)
set(iterable)
str(object='')
str(objec­t=b'', encodi­ng=­'ut­f-8', errors­='s­trict')
tuple(iterable)

Built-in math functions

abs(x)
divmod(a, b)
max(iterable, *, default, key=None)
max(arg1, arg2, *args, key=None)
min(iterable, *, default, key=None)
min(arg1, arg2, *args, key=None)
pow(base, exp, mod=None)
round(number, ndigit­s=None)
sum(iterable, /, start=0)

String built-in functions

bin(x)
chr(i)
hex(x)
oct(x)
ord(c)
print(*objects, sep=' ', end='\n', file=None, flush=­False)

Functional progra­mming

filter(function, iterable)
map(function, iterable, *itera­bles)
func = lambda a, b, c : a + b + c

Other built-in functions

all(iterable)
any(iterable)
enumerate(iterable, start=0)
sorted(iterable, /, *, key=None, revers­e=F­alse)
zip(*iter­ables, strict­=False)

Misc

occurrence
import collections
d = defaultdict(int)
for w in words:
d[w] += 1
 

Min Max

min int/float
float('-inf')
// or
-math.inf
max int/float
float('inf')
// or
math.inf
min
m = min(a, b, c, ...)
min in array
m = min(arr)
min in dict key
m = min({1:4, 2:3}) # 1
dict key w/ min value
d = {1:4, 2:3}
m = min(d, key = lamba k : d[k]) # 2

String

new
s = "­str­"
get
c = s[i]
check empty
if not s:
length
length = len(s)
compare
if s1 == s2:
reverse
r = s[::-1]
to lower
s = s.lower()
to upper
s = s.upper()
get sub string
sub = s[from : to]
check sub string
if sub in s:
split
arr = s.split(sep)
join
s = sep.join(arr)

List

new
arr = [1, 2, 3]
get
num = arr[i]
check empty
if not arr:
length
length = len(arr)
reverse
r = arr[::-1]
get sub array
sub = arr[from : to]
fill
arr = [i for i in range(5)]
traverse
for num in arr:
sort asscending (in-place)
arr.sort()
sort descending (in-place)
arr.sort(rever­se=­True)
find index
index = arr.index(num, start, end)

Stack

new
stack = []
push
stack.append(num)
pop
popped = stack.pop()
top
top = stack[-1]
check empty
if not stack:
length
length = len(stack)

Queue

new
queue = []
push
queue.append(num)
pop
popped = queue.pop(0)
front
front = queue[0]
check empty
if not queue:
length
length = len(queue)
 

Heap

import
import heapq
new
heapq = []
heapify
heapq.heapify(heap)
push
heapq.heappush(heap, item)
pop
smallest = heapq.heappop(heap)
push & pop
smallest = heapq.heappu­shpop(heap, item)
pop & push
smallest = heapq.heapre­place(heap, item)
peek
smallest = heap[0]
check empty
if not queue:
length
length = len(queue)

Set

new
s = set() # for empty set
# or
s = {1, 2, 3}
add
s.add(item)
add list
s.update(arr)
delete
s.remove(item) # throw error
# or
s.discard(item) # no error
clear
s.clear()
check empty
if not s:
check in set
if item in s:
size
length = len(s)
to list
arr = list(s)
merge
s = s1 | s2
inters­ection
s = s1 & s2
difference
s = s1 - s2
symetric difference
s = s1 ^ s2

Dict

new
d = {} # for empty dict
# or
d = {1:2, 3:4}
set
d[key] = val
get
val = d[key] # throws error
# or
val = d.get(key) # None if not exist
delete
val = s.pop(key)
# or
del d[key]
delete last
key, val = s.popitem()
clear
del d
check empty
if not d:
check key in dict
if key in d.keys():
check value in dict
if val in d.values():
size
length = len(s)
iterate
for key, val in d.items():

Queue (thread safe)

import
from queue import Simple­Queue
new
queue = SImple­Queue()
push
queue.put(num)
pop
popped = queue.get()
check empty
if queue.empty():
length
length = queue.qsize()

Priori­tyQueue (thread safe)

import
from queue import Priori­tyQueue
new
pq = Priori­tyQ­ueue()
push
pq.put(num)
pop
popped = pq.get()
check empty
if pq.empty():
length
length = pq.qsize()