Python3 Cheatsheet

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# Modules and Packages
import module_name
from module_name import function_name
from module_name import *

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# Variables and Data Types
intVar = 10
strVar = "Some text"
boolVar = True
floatVar = 3.14
listVar = [1, 3, 5, "Text element", 3.4526]
multidimListVar = [ [[2,3,4],[6,7,8],[10,15,20]] , [[11,22,33],[66,77,88],[100,150,200]] , [[0,-1,-2],["strange","c",3.14],[2,2,2]] ]
tupleVar = (1, 4, 6, 7)
dictVar = {"key":"value", "4":"value2", "Some key data": "Some value data"}

# Integer Variable Base
decVar = 423
hexVar = 0xfe34
binVar = 0b0110101
octVar = 0o3216

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# Arithmetics
a = 45
b = 3
resA = a+b     # Sum
resB = a-b     # Subtraction
resC = a*b     # Multiplication
resD = a/b     # Integer division
resE = a**b    # Power (a^b)
resF = a%b     # Modulus

# Bitwise Operators
a = 0x01f3
b = 0x243
resA = a&b     # Bitwise AND
resB = a|b     # Bitwise OR
resC = a^b     # Bitwise XOR
resD = ~a      # Bitwise NOT
resE = a<<3    # Left shift
resF = a>>3    # Right shift

# Shorthand Operators
a += 32        # Update a with the result of a+32
a -=45         # Update a with the result of a-45
a *= 21        # Update a with the result of a/21
a /= 12        # Update a with the result of a/12
a &= 0b11110   # Update a with the result of a&0b11110
a |= 0x3fe     # Update a with the result of a|0x3fe
a ^= 0x43f     # Update a with the result of a^0x43f
a <<= 3        # Update a with the result of a<<3
a >>= 2        # Update a with the result of a>>2

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#Strings
strVar = "Here's a string!"
strVar = strVar + " Now I'm adding another string!"
substrVar1 = strVar[:17]    # substrVar1 contains characters from the 1st (included) to the 17th character (not included)
substrVar2 = strVar[18:]    # substrVar1 contains characters from the 18th (included) to the last character (included)
substrVar3 = strVar[10:16]  # substrVar1 contains characters from the 10th (included) to the 16th character (not included)
tokensVar1 = strVar.split(" ")      # Split string with the given character; this returns a list
tokensVar2 = strVar.split(" ",2)    # Split string with the given character with a maximum of 2 times (first 2 occurrences)
newStrVar1 = strVar.replace("!","!!!")   # Replace all occurrences of a char sequence with another char sequence
newStrVar2 = strVar.replace("!","!!!",1) # Replace just the first occurrence of a char sequence with another char sequence

# Lists
listVar = [2, 3, 4, 5, 6, 7, 2, 2, 8, 9, 10]
listVar.pop()              # Remove the last item from the list
listVar.append(10)         # Append 10 as last item
listVar.count()            # Return the number of items in the list
listVar.remove(2)          # Remove the first occurrence of element 2
listVar.sort()             # Sort in ascending order
listVar.sort(reverse=True) # Sort in descending order
listVar = ["a", "ab", "abcdef", "abc", "abcdefghi"]
listVar.sort(key=len)      # String length based ascending order
newList = listVar[:2]     # newList contains elements of listVar from the 1st (included) to the 2nd one (not included)
newList = listVar[2:]     # newList contains elements of listVar from the 2nd (included) to the last one (included)
newList = listVar[2:3]    # newList contains elements of listVar from the 2nd (included) to the 3rd one (not included)

# Tuples - immutable list of elements
tupleVar = ("Some prime number", 2, 3, 5, 7, 11, 13, 17, 23, "Some float number", 3.14, 2.7) # Tuple definition. It can't be changed anymore!
nOccurr2 = tupleVar.count(2)    # Return the number of occurrences of element 2
indexOf2 = tupleVar.index(2)    # Return the index of first occurrence of element 2
anotherTuple = tupleVar[3:6]    # anotherTuple contains tupleVar elements, from the 3rd (included) to the sixth (not included)
tupleVar[4] = 9                 # THIS RAISES AN ERROR!

# Dictionaries
dictVar = {"Name":"John", "Surname":"Clayton", "Age":35, "Height"=1.81, "Signs":["Glasses", "Blonde-haired"]}
dictValue = dictVar["Name"]         # Get the value of a key
dictValue = dictVar.get("Name")     # Get the value of a key
dictVar["Name"] = "Michael"         # Update a value
dictVar.update({"Name":"Michael"})  # Update a value
dictVar["Foot"] = 8                 # Add a pair
dictVar.update({"Foot":8})          # Add a pair
values = dictVar.values()           # Returns all dictVar values 
keys = dictVar.keys()               # Returns all dictVar keys
dictVar.pop("Name")                 # Removes the key:value pair with specified key
dictVar.popitem()                   # Removes the last inserted pair
dictVar.clear()                     # Empties the whole dictionary

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# if-else Control Flow
if condition:
    # code block
elif another_condition:
    # code block
else:
    # code block

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# for Loop
for item in iterable:
    # code block
    if condition:
        #code block
        continue
    else:
        #code block
        break

# while Loop    
while condition:
    # code block
    if condition:
        #code block
        continue
    else:
        #code block
        break

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# Functions
def my_function(param1, param2=default_value):
    # code block
    return result

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# Exception Handling
try:
    # code block
except ExceptionType1 as e1:
    # handle exception1
except ExceptionType2 as e2:
    # handle exception2
except:
    # handle all the remaining exceptions
else:
    # code executed if no exception is risen
finally:
    # code always executed, both if an exception is risen or not

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# This is a single-line comment

"""
This is a
multi-line comment
"""

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user_input = input("Enter something: ")
print("You entered: ", user_input)

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#File Handling

"""
filename is a string containing the path+name of the file to be opened
mode can be r=read-only (default), w=write-only (old file with same name is replaced) 
            a=append, r+ = read-and-write, rb/wb/ab=read/write/append in binary mode
encoding is a string thta specifies the encoding of the file
"""

"""
Preferable way to open a file 
In this way, file is safely written, then closed (you don't have to call fp.close())
"""
with open(filename, mode, encoding) as fp:    
    # Do something with fp      

"""    
Another way to open a file
In this way, if close() is called immediately after write(), file could be closed before
all data is written! Use the first way instead
"""
fp = open(filename, mode,encoding)

fp.close()                  # Close the file, saving all modifications
fp.write("Hello, World!")   # Write the specified string in the file pointed by fp
fp.writelines(stringList)   # Write a list of strings (you must append \n to each line)
content = fp.read()         # Read the whole file content and store it in a variable
row = fp.readline()         # Read just one line of the file (read till \n)
rows = fp.readlines()       # Returns a list where elements are lines (split using \n as needle)
fp.seek(byteNumber)         # Move the file cursor to byteNumber position of the file
byteNumber = fp.tell()      # Return the position of the cursors

# Alternative way to read and elaborate one line at a time
for line in fp:
    # Do something with line