Python Reference

Essential Python commands, functions, and concepts for beginners and developers.

>Variables

Variables

Store information.

name = "Sam"

type()

Checks data type.

type(name)

int()

Converts to integer.

int("5")

float()

Converts to decimal.

float("5.2")

str()

Converts to string.

str(100)

>Output & Input

print()

Displays output.

print("Hello")

input()

Gets user input.

name = input()

f-strings

Insert variables into text.

f"Hello {name}"

>Math

+

Add numbers.

5 + 2

-

Subtract numbers.

10 - 3

*

Multiply numbers.

4 * 5

/

Divide numbers.

20 / 4

//

Floor division.

10 // 3

%

Remainder operator.

10 % 3

**

Power operator.

2 ** 3

round()

Rounds number.

round(4.7)

abs()

Absolute value.

abs(-5)

>Strings

len()

String length.

len("Hello")

.upper()

Uppercase text.

"hello".upper()

.lower()

Lowercase text.

"HELLO".lower()

.replace()

Replace text.

"Hi".replace("H","B")

.split()

Splits string.

"a,b".split(",")

.strip()

Removes spaces.

" hi ".strip()

>Conditions

if

Runs code if true.

if age > 18:

elif

Another condition.

elif age > 10:

else

Alternative code.

else:

==

Equal comparison.

5 == 5

>

Greater than.

10 > 5

<

Less than.

2 < 5

and

Both conditions true.

x > 1 and y > 1

or

One condition true.

x > 1 or y > 1

not

Reverses condition.

not True

>Loops

for

Repeats code.

for x in range(5):

while

Loops while true.

while x < 5:

range()

Creates number range.

range(10)

break

Stops loop.

break

continue

Skips loop step.

continue

>Functions

def

Creates function.

def test():

return

Returns value.

return total

Parameters

Function inputs.

def add(a,b):

lambda

Short function.

lambda x: x+1

>Lists

[]

Creates list.

fruits = []

.append()

Adds item.

fruits.append("Apple")

.remove()

Removes item.

fruits.remove("Apple")

.pop()

Removes last item.

fruits.pop()

len()

List size.

len(fruits)

sorted()

Sorts list.

sorted(numbers)

>Dictionaries

{}

Creates dictionary.

user = {}

Dictionary Key

Stores value.

user["name"] = "Sam"

.keys()

Gets keys.

user.keys()

.values()

Gets values.

user.values()

.items()

Gets keys and values.

user.items()

>Files

open()

Opens file.

open("file.txt")

.read()

Reads file.

file.read()

.write()

Writes to file.

file.write("Hello")

with

Safely handles files.

with open() as file:

>Modules

import

Imports module.

import math

from

Imports part of module.

from math import sqrt

math.sqrt()

Square root.

math.sqrt(25)

random.randint()

Random number.

random.randint(1,10)

>Error Handling

try

Tests code for errors.

try:

except

Handles errors.

except:

finally

Runs after try.

finally: