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Python 3 Beginner's Reference Cheat Sheet by

Python 3 Beginner's reference

Operators

Assignment
=
Arithmetic
+, -, *, /, %
Comparison
>, >=, <, <=, ==, !=
Logical
not, and, or

String operations (string s)

s.coun­t(s­ubs­tring)
Count occurences
s.find­(su­bst­ring)
Index of first occurence
s.join­(se­quence)
Concat­enate sequence
s.spli­t([­del­imi­ter])
Split into list

List operations (list l, element e)

l.appe­nd(e)
Add e
l.remo­ve(e)
Remove e
l.pop(e)
Remove and return e
l.count(e)
Count occurences
l.reve­rse()
Reverse l
l.sort()
Sort l

Dictionary operations (dict d, key k)

d.clear()
Clear d
d.get(k)
Return d[k]
d.keys()
Return keys in d
d.values()
Return values in d
d.items()
Return key-value pairs in d
 

File operations (file f)

f = open(path)
Open f
f.read()
Read f
f.read­line()
Read line from f
f.read­lines()
Return list of lines in f
f.write(s)
Write s to f
f.close()
Close f

In-built functions

int(), float(), str(), bool()...
Type casting
len(data)
Length
min(va­lues), max(va­lues)
Minimum / Maximum
pow(x,y, [z])
X to the power Y [mod Z]
range(­start, stop, [step])
Ordered list
input(), print()
Console Input/­Output
filter­(fu­nction, array)
Filter array
map(fu­nction, array)
Map function onto array
id(object)
Unique object ID
round(n, [x])
Round n [x decimal places]

Module import

import module
from module import submodule
 

Control Flow

if(cond): <co­de> else: <co­de>
If-else
if(cond1): <co­de> elif(c­ond1): <co­de> else: <co­de>
If-eli­f-else
for i in range(­[st­art], stop, [step]): <co­de>
For loop over range
for i in items: <co­de>
For loop over iterable
while(­con­dit­ion): <co­de>
While loop
break
Exit first enclosing loop
continue
Skip to next iteration

Useful standard library modules

math, numpy, scipy
Math
matplotlib
Graph plotting
random
Random generators
datetime
Date and time
timeit
Perfor­mance
re
Regular expres­sions
os
OS intera­ction
sys
stdin, stdout, stderr, version
urllib
Internet access
zlib
Data compre­ssion

Object­-or­iented

class Person:
Class definition
x = Person­(age, height)
Object creation
x.age
Field access
x.birt­hday()
Method access
                   
 

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