Python Cheat Sheet 2019

Return to site

Python Cheat Sheet 2019

By Stef Maruch, Aahz Maruch. New to programming in Python? Whether you're working with string methods or built-in functions in Python, this Cheat Sheet helps you program the correct order for the operation so you achieve the correct result. Not only this, Python being a high-level language it has plenty of libraries to that make your work easier, libraries for data analysis, computer vision, web development and more. Download Python 3 Beginners Cheat Sheet. Join Python Programming Bootcamp. Dependencies and Setup¶. In the Python code we assume that you have already run import numpy as np. In the Julia, we assume you are using v1.0.2 or later with Compat v1.3.0 or later and have run using LinearAlgebra, Statistics, Compat.

Python Cheat Sheet 3MATLAB–Python–Julia cheatsheet
Dependencies and Setup¶In the Python code we assume that you have already run importnumpyasnp

Python Cheat Sheet 3MATLAB–Python–Julia cheatsheet
Dependencies and Setup¶In the Python code we assume that you have already run importnumpyasnp
In the Julia, we assume you are using v1.0.2 or later with Compat v1.3.0 or later and have run usingLinearAlgebra,Statistics,Compat
Creating Vectors¶Operation
MATLAB
Python
Julia
Row vector: size (1, n)
Column vector: size (n, 1)
1d array: size (n, )
Not possible
or
Integers from j to n withstep size k
Linearly spaced vectorof k points
Creating Matrices¶Operation
MATLAB
Python
Julia
Create a matrix
2 x 2 matrix of zeros
2 x 2 matrix of ones
2 x 2 identity matrix
Diagonal matrix
Uniform random numbers
Normal random numbers
Sparse Matrices
Tridiagonal Matrices
Manipulating Vectors and Matrices¶Operation
MATLAB
Python
Julia
Transpose
Complex conjugate transpose(Adjoint)
Concatenate horizontally
or
or
Concatenate vertically
or
or
Reshape (to 5 rows, 2 columns)
Convert matrix to vector
Flip left/right
Flip up/down
Repeat matrix (3 times in therow dimension, 4 times in thecolumn dimension)
Preallocating/Similar
N/A similar type
Broadcast a function over acollection/matrix/vector
Functions broadcast directly
Functions broadcast directly
Accessing Vector/Matrix Elements¶Operation
MATLAB
Python
Julia
Access one element
Access specific rows
Access specific columns
Remove a row
Diagonals of matrix
Get dimensions of matrix
Mathematical Operations¶Operation
MATLAB
Python
Julia
Dot product
Matrix multiplication
Final cut pro 10 4 1. Inplace matrix multiplication
Not possible
Element-wise multiplication
Matrix to a power
Matrix to a power, elementwise
Inverse
or
or
Determinant
Eigenvalues and eigenvectors
Euclidean norm
Solve linear system(Ax=b) (when (A)is square)
Solve least squares problem(Ax=b) (when (A)is rectangular)
Sum / max / min¶Operation
MATLAB
Python
Julia
Sum / max / min ofeach column
Sum / max / min of each row
Sum / max / min ofentire matrix
Cumulative sum / max / minby row
Cumulative sum / max / minby column
Programming¶Operation
MATLAB
Python
Julia
Comment one line
Comment block
For loop
While loop
If
If / else
Print text and variable
Function: anonymous
Function
Tuples
Can use cells but watch performance
Named Tuples/Anonymous Structures
Closures
Inplace Modification
No consistent or simple syntaxto achieve this
New to programming in Python? No worries. Whether you're working with string methods or built-in functions in Python, this Cheat Sheet helps you program the correct order for the operation so you achieve the correct result.
Python String MethodsThe following list shows you how to perform common string methods, or actions on a string, in Python. Type the specific order to achieve the desired result.
SyntaxAction
S.count(substring[, start[, end]])Count occurrences of substring
S.decode([encoding])Decode to Unicode using default encoding
S.encode([encoding])Encode from Unicode using default encoding
S.endswith(suffix[, start[, end]])True if S ends with suffix
S.find(substring [,start [,end]])Find first occurrence of substring and return its index
number; if not found, return -1
S.index(substring [,start [,end]])Find first occurrence of substring and return its index
number; if not found, raise ValueError
S.isalnum()True if S has only alphanumeric characters
S.isalpha()True if S has only alphabetic characters
S.isdigit()True if S has only digits
S.isspace()True if S has only whitespace characters
S.join(iterable)Using S as a separator, stick together the strings in
iterable
S.lower()Convert S to lowercase
S.lstrip([chars])Remove whitespace (or chars) from front (left) of
S
S.replace (old, new[, count])Replace old (a substring) with new
S.rfind(substring [,start [,end]])Find the last (rightmost) occurrence of substring and
return its index number; if not found, return -1
S.rindex(substring [,start [,end]])Find the last (rightmost) occurrence of substring and
returns its index number; if not found, raise ValueError
S.rstrip([chars])Remove whitespace (or chars) from end (right) of
S
S.split([separator [,maxsplit]])Split S using whitespace (or separator) and
return a list of substrings
S.startswith(prefix[, start[, end]])True if S starts with prefix
S.strip([chars])Remove characters at beginning and end of S; default is
whitespace characters
S.upper()Convert S to uppercase
Note: String methods that change a string always
return a copy; the original string remains unchanged.
Python's Built-In FunctionsBuilt into the Python interpreter are a number of functions (pieces of code that carry out specific operations and return the results of those operations), including math functions other than the standard arithmetic operators. Here's a list of Python's built-in functions along with their pattern and corresponding action:
SyntaxAction
abs(number)Return absolute value of number
all(iterable)Return True unless at least one element is false
any(iterable)Return False unless at least one element is true
chr(integer)Return the character with the specified ASCII value (must be
between 0 and 256)
delattr(object, name), del x.yDelete the named attribute from object
dir([object])Return the names in the current namespace or object‘s
namespace
eval(source[, globals[, locals]])Execute source as a Python expression
getattr(object, name[, default]) x.yReturn specified attribute (name) of object,
raising AttributeError if not found; optional: return
default if name doesn't exist
globals()Return dict of global names in the current namespace
hasattr(object, name)True if object has the specified attribute
(name)
isinstance(object, class-or-type)True if object is an instance of the specified class (or
its subclasses) or type; optional: specify multiple classes or
types using a tuple
issubclass(C, B)True if class C is a subclass of class B;
optional: specify multiple classes using a tuple
iter(iterable)Return an iterator over iterable
len(object)Return number of items in a sequence or dict
locals()Return dictionary of local names in the current namespace
max(iterable), max(a, b, c, …)Return largest item of iterable or argument list
min(iterable), min(a, b, c, …)Return smallest item of iterable or argument list
ord(char)Return the ASCII value of a one-character string
range([start,] stop[, step])Return a list of integers from 0 up to (but not
including) stop
Python Cheat Sheet Pdfraw_input([prompt])Return a string from standard input (usually something the user
types), not including the newline character
repr(object)Return canonical string representation of object
round(number[, ndigits])Return floating-point number rounded to nearest integer
setattr(object, name, value) x.y = vSet object‘s attribute to the specified value
sorted(iterable[, cmp [, key [, reverse])Return a new sorted list; optional: cmp and key
take functions as arguments; reverse=True
sum(iterable[, start=0])Return the sum of all elements of iterable; does not
work with strings
unichr(integer)Return a Unicode string corresponding to integer, which
must be between 0 and 0x10ffff
xrange([start,] stop[, step])Return an iterable that generates a range from 0 up to
(but not including) stop
zip([iter1 [, iter2 [, …]]])Take zero or more iterables and return a list of tuples that
group the items at a particular index number; the list returned is
the same length as the shortest iterable

Operation	MATLAB	Python
Row vector: size (1, n)
Column vector: size (n, 1)
1d array: size (n, )	Not possible	or
Integers from j to n withstep size k
Linearly spaced vectorof k points

Operation	MATLAB	Python	Julia
Create a matrix
2 x 2 matrix of zeros
2 x 2 matrix of ones
2 x 2 identity matrix
Diagonal matrix
Uniform random numbers
Normal random numbers
Sparse Matrices
Tridiagonal Matrices

Operation	MATLAB	Python
Transpose
Complex conjugate transpose(Adjoint)
Concatenate horizontally	or	or
Concatenate vertically	or	or
Reshape (to 5 rows, 2 columns)
Convert matrix to vector
Flip left/right
Flip up/down
Repeat matrix (3 times in therow dimension, 4 times in thecolumn dimension)
Preallocating/Similar	N/A similar type
Broadcast a function over acollection/matrix/vector	Functions broadcast directly	Functions broadcast directly

Operation	MATLAB	Python	Julia
Access one element
Access specific rows
Access specific columns
Remove a row
Diagonals of matrix
Get dimensions of matrix

Operation	MATLAB	Python
Dot product
Matrix multiplication
Final cut pro 10 4 1. Inplace matrix multiplication	Not possible
Element-wise multiplication
Matrix to a power
Matrix to a power, elementwise
Inverse	or	or
Determinant
Eigenvalues and eigenvectors
Euclidean norm
Solve linear system(Ax=b) (when (A)is square)
Solve least squares problem(Ax=b) (when (A)is rectangular)

Operation	MATLAB	Python	Julia
Sum / max / min ofeach column
Sum / max / min of each row
Sum / max / min ofentire matrix
Cumulative sum / max / minby row
Cumulative sum / max / minby column

Operation	MATLAB	Python	Julia
Comment one line
Comment block
For loop
While loop
If
If / else
Print text and variable
Function: anonymous
Function
Tuples	Can use cells but watch performance
Named Tuples/Anonymous Structures
Closures
Inplace Modification	No consistent or simple syntaxto achieve this

Syntax	Action
S.count(substring[, start[, end]])	Count occurrences of substring
S.decode([encoding])	Decode to Unicode using default encoding
S.encode([encoding])	Encode from Unicode using default encoding
S.endswith(suffix[, start[, end]])	True if S ends with suffix
S.find(substring [,start [,end]])	Find first occurrence of substring and return its index number; if not found, return -1
S.index(substring [,start [,end]])	Find first occurrence of substring and return its index number; if not found, raise ValueError
S.isalnum()	True if S has only alphanumeric characters
S.isalpha()	True if S has only alphabetic characters
S.isdigit()	True if S has only digits
S.isspace()	True if S has only whitespace characters
S.join(iterable)	Using S as a separator, stick together the strings in iterable
S.lower()	Convert S to lowercase
S.lstrip([chars])	Remove whitespace (or chars) from front (left) of S
S.replace (old, new[, count])	Replace old (a substring) with new
S.rfind(substring [,start [,end]])	Find the last (rightmost) occurrence of substring and return its index number; if not found, return -1
S.rindex(substring [,start [,end]])	Find the last (rightmost) occurrence of substring and returns its index number; if not found, raise ValueError
S.rstrip([chars])	Remove whitespace (or chars) from end (right) of S
S.split([separator [,maxsplit]])	Split S using whitespace (or separator) and return a list of substrings
S.startswith(prefix[, start[, end]])	True if S starts with prefix
S.strip([chars])	Remove characters at beginning and end of S; default is whitespace characters
S.upper()	Convert S to uppercase
*Note:* String methods that change a string always return a copy; the original string remains unchanged.

Syntax	Action
abs(number)	Return absolute value of number
all(iterable)	Return True unless at least one element is false
any(iterable)	Return False unless at least one element is true
chr(integer)	Return the character with the specified ASCII value (must be between 0 and 256)
delattr(object, name), del x.y	Delete the named attribute from object
dir([object])	Return the names in the current namespace or object‘s namespace
eval(source[, globals[, locals]])	Execute source as a Python expression
getattr(object, name[, default]) x.y	Return specified attribute (name) of object, raising AttributeError if not found; optional: return default if name doesn't exist
globals()	Return dict of global names in the current namespace
hasattr(object, name)	True if object has the specified attribute (name)
isinstance(object, class-or-type)	True if object is an instance of the specified class (or its subclasses) or type; optional: specify multiple classes or types using a tuple
issubclass(C, B)	True if class C is a subclass of class B; optional: specify multiple classes using a tuple
iter(iterable)	Return an iterator over iterable
len(object)	Return number of items in a sequence or dict
locals()	Return dictionary of local names in the current namespace
max(iterable), max(a, b, c, …)	Return largest item of iterable or argument list
min(iterable), min(a, b, c, …)	Return smallest item of iterable or argument list
ord(char)	Return the ASCII value of a one-character string
range([start,] stop[, step])	Return a list of integers from 0 up to (but not including) stop

raw_input([prompt])	Return a string from standard input (usually something the user types), not including the newline character
repr(object)	Return canonical string representation of object
round(number[, ndigits])	Return floating-point number rounded to nearest integer
setattr(object, name, value) x.y = v	Set object‘s attribute to the specified value
sorted(iterable[, cmp [, key [, reverse])	Return a new sorted list; optional: cmp and key take functions as arguments; reverse=True
sum(iterable[, start=0])	Return the sum of all elements of iterable; does not work with strings
unichr(integer)	Return a Unicode string corresponding to integer, which must be between 0 and 0x10ffff
xrange([start,] stop[, step])	Return an iterable that generates a range from 0 up to (but not including) stop
zip([iter1 [, iter2 [, …]]])	Take zero or more iterables and return a list of tuples that group the items at a particular index number; the list returned is the same length as the shortest iterable