Python Cheatsheet & Wiki

Tips

• Modules ¹
  • Import modules at top of file I.e. import mymodule
  • Module functions are called in code with modulename.function. Example: mymodule.greeting("Jonathan")

Operators

Arithmetic

Arithmetic operators are used with numeric values to perform common mathematical operations:

Operator	Name	Example	Try it
+	Addition	x + y	Try it »
-	Subtraction	x - y	Try it »
*	Multiplication	x * y	Try it »
/	Division	x / y	Try it »
%	Modulus	x % y	Try it »
**	Exponentiation	x ** y	Try it »
//	Floor division	x // y	Try it

Python Assignment Operators

Assignment operators are used to assign values to variables:

Operator	Example	Same As	Try it
=	x = 5	x = 5	Try it »
+=	x += 3	x = x + 3	Try it »
-=	x -= 3	x = x - 3	Try it »
*=	x *= 3	x = x * 3	Try it »
/=	x /= 3	x = x / 3	Try it »
%=	x %= 3	x = x % 3	Try it »
//=	x //= 3	x = x // 3	Try it »
**=	x **= 3	x = x ** 3	Try it »
&=	x &= 3	x = x & 3	Try it »
|=	x |= 3	x = x | 3	Try it »
^=	x ^= 3	x = x ^ 3	Try it »
>>=	x >>= 3	x = x >> 3	Try it »
<⇐	x <⇐ 3	x = x << 3	Try it »
:=	print(x := 3)	x = 3 print(x)	Try it »

Python Comparison Operators

Comparison operators are used to compare two values:

Operator	Name	Example	Try it
==	Equal	x == y	Try it »
!=	Not equal	x != y	Try it »
>	Greater than	x > y	Try it »
<	Less than	x < y	Try it »
>=	Greater than or equal to	x >= y	Try it »
⇐	Less than or equal to	x ⇐ y	Try it »

Python Logical Operators

Logical operators are used to combine conditional statements:

Operator	Description	Example	Try it
and	Returns True if both statements are true	x < 5 and  x < 10	Try it »
or	Returns True if one of the statements is true	x < 5 or x < 4	Try it »
not	Reverse the result, returns False if the result is true	not(x < 5 and x < 10)	Try it »

Python Identity Operators

Identity operators are used to compare the objects, not if they are equal, but if they are actually the same object, with the same memory location:

Operator	Description	Example	Try it
is	Returns True if both variables are the same object	x is y	Try it »
is not	Returns True if both variables are not the same object	x is not y	Try it »

Python Membership Operators

Membership operators are used to test if a sequence is presented in an object:

Operator	Description	Example	Try it
in	Returns True if a sequence with the specified value is present in the object	x in y	Try it »
not in	Returns True if a sequence with the specified value is not present in the object	x not in y	Try it »

Python Bitwise Operators

Bitwise operators are used to compare (binary) numbers:

Operator	Name	Description	Example	Try it
&	AND	Sets each bit to 1 if both bits are 1	x & y	Try it »
|	OR	Sets each bit to 1 if one of two bits is 1	x | y	Try it »
^	XOR	Sets each bit to 1 if only one of two bits is 1	x ^ y	Try it »
~	NOT	Inverts all the bits	~x	Try it »
<<	Zero fill left shift	Shift left by pushing zeros in from the right and let the leftmost bits fall off	x << 2	Try it »
>>	Signed right shift	Shift right by pushing copies of the leftmost bit in from the left, and let the rightmost bits fall off	x >> 2	Try it »

Conditional Statements

If

Python supports the usual logical conditions from mathematics (see Operators)

These conditions can be used in several ways, most commonly in “if statements” and loops.

An “if statement” is written by using the if keyword.

Example

In this example we use two variables, a and b, which are used as part of the if statement to test whether b is greater than a. As a is 33, and b is 200, we know that 200 is greater than 33, and so we print to screen that “b is greater than a”.

a = 33  
b = 200  
if b > a:  
   print("b is greater than a")
 ```

Elif

The elif keyword is Python’s way of saying “if the previous conditions were not true, then try this condition”.

Example

In this example a is equal to b, so the first condition is not true, but the elif condition is true, so we print to screen that “a and b are equal”.

a = 33  
b = 33
if b > a:
	print("b is greater than a")
elif a == b:
	print("a and b are equal")

Else

The else keyword catches anything which isn’t caught by the preceding conditions.

Example

In this example a is greater than b, so the first condition is not true, also the elif condition is not true, so we go to the else condition and print to screen that “a is greater than b”.

You can also have an else without the elif.

a = 200  
b = 33
if b > a:
	print("b is greater than a")
elif a == b:
	print("a and b are equal")
else:
	print("a is greater than b")

Short-Hand If

If you have only one statement to execute, you can put it on the same line as the if statement.

Example

if a > b: print("a is greater than b")

Short-Hand If … Else

If you have only one statement to execute, one for if, and one for else, you can put it all on the same line:

Example

a = 2
b = 330
print("A") if a > b else print("B")

And, Or, and Not

The and keyword is a logical operator, and is used to combine conditional statements:

Example

Test if a is greater than b, AND if c is greater than a:

a = 200  
b = 33  
c = 500  
if a > b and c > a: 
	print("Both conditions are True")

The or keyword is a logical operator, and is used to combine conditional statements:

Example

Test if a is greater than b, OR if a is greater than c:

a = 200
b = 33
c = 500
if a > b or a > c:
	print("At least one of the conditions is True")

The not keyword is a logical operator, and is used to reverse the result of the conditional statement:

Example

Test if a is NOT greater than b:

a = 33
b = 200
if not a > b:
	print("a is NOT greater than b")

More Conditional Statements

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Loops

A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).

Examples

Print each fruit in a fruit list:

fruits = ["apple", "banana", "cherry"]  
for x in fruits:  
  print(x)

Loop through the letters in the word “banana”:

for x in "banana":  
  print(x)

Exit the loop when x is “banana”:

fruits = ["apple", "banana", "cherry"]  
for x in fruits:  
  print(x)  
  if x == "banana":  
    break

Exit the loop when x is “banana”, but this time the break comes before the print:

fruits = ["apple", "banana", "cherry"]  
for x in fruits:  
  if x == "banana":  
    break  
  print(x)

More for loops

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Footnotes

Footnotes

1. More info here ↩