Coding Cheat Sheet

A cheat sheet in English by J2003J

-python

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Input & Output

Output a message to the user

print("Hello There")

Ask the user for a text input (string)

name = input("What is your name?")

Ask the user for a number input (Integer)

age = int(input("How old are you?"))

Add a new line

name = input("What is your name?\n")

Concatenate strings

print("Hello "+ name )

Concatenate different data types

print("You are",age ,"years old")

Output the first letter

print(name[0])

Uppercase/Lowercase format

print(name.upper()) | print(name.lower())

Uppercase then lowercase format

print(name[0].upper()+name[1:].lower())

IF Statements

IF
x = 3
if x == 3:
print("x = 3")
__________________
IF / ELSE
x = 7
if x > 8:
print("Yes")
else:
print("No")
__________________
ELIF
x = 4
if x > 8:
print("A")
elif x > 5:
print("B")
elif x > 2:
print("C")
else:
print("F")

Remember to indent your code [Press the 'Tab' button n the keyboard]

Editing Lists

Replace third item

mylist[2] = 43

Insert in position

mylist.insert(1, "OCR")

Add to the end of a list

mylist.append("GCSE")

Remove all Sciences

mylist.remove("Science)

Delete all items

mylist = []

Delete third item

del mylist[2]

Reverse list order

mylist.reverse()

Sort list order

mylist.sort()

Join items using a space

print(" ".join(mylist))

Dictionaries

Creating a dictionary

mydict = {"a":1, "b":2, "c":3}

Returns the value of b

mydict["b"]

Check in dictionary

"c" in mydict

Display the keys

mydict.keys()

Display keys and items

mydict,items()

Inequalities

Equal to

x == 3

Not equal to

x != 4

Less than / equal to

x <= 2

More than / equal to

x >= 1

Between two numbers

<= 3 x <= 12

AND

x == 1 and z == 4

x == "A" or x == "a"

For Loop

Repeat 5 times
for x in range (5):
print("Owen")
_________________
Repeat length of string
for x in "Nathan":
print(x)
_________________
Count from 1 to 10
for x in range (1,11):
print(x)
_________________
Count from 1 to 10 in 2's
for x in range (1,11,2):
print(x)

Repeats code a predefined number of times

While Loops

Repeat until false
while True:
print("Hello There!")
____________________
Using 'break' to end the loop
while True:
x = input("Say Yes")
if x == "Yes":
break
____________________
Until x is more than 100
x = 0
while x < 100:
x = int(input("x ?"))

A while loop will repeat infinitely until the program or user input tells it to stop
Repeats code until a condition is met [within the program]

Creating And Using Files

Create document

myfile = open("Filename.txt","w")

Add data to the text file

myfile.write("Hello World")

Reads entire file into one string

myfile.read()

Reads first 4 characters into one string

myfile.read(4)

Reads one line of a file

myfile.readline()

Reads entire file into a list of strings, one per line

myfile.readlines()

Steps through lines in a file

for eachline in myfile:

Close the file

myfile.close()

("w" write, "r" read, "a" append)
.csv will create a spreadsheet

Demonstrating knowledge

Annotate / Comment on a line of code

#short comments

Annotate / comment on a block of code

'''for longer comments'''

Always annotate you code

Variables

Creating a variable

name = "Josh"

Length of string

len(name)

Print a variable

print(name)

Coverting [String↔Integer]

str(age) 'or' int(age)

All variables are strings [str] by default

Numbers

Addition

2+2

Subtraction

4-1

Multiplication

3*5

Division

15/10

To the power of...

1.5**2

Multiplying A String

"Ethan" *14

Numbers follow the BIDMAS / BODMAS rule

Creating And Accessing Lists

Creating a list

mylist = ["Computer", "Science", 17]

Output full list

print(mylist)

Access first item

mylist[0]

Access first to second

mylist[1:2}

Access third item to the end

mylist[2:]

Access up to the third item

mylist[:2]

Check for in list

"Computer" in mylist

Concatenate

mylist + ["a"]

Remove third item and use

mylist.pop(2)

Remove last item and use

mylist.pop()

Find position in the list

mylist.index(Science)

Count appearances

mylist.count(17)

Add values

sum(mylist)

Length of List

len(mylist)

Compare lists

cmp(mylist, list)

Biggest number in list

max(mylist)

Smallest number in list

min(mylist)

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