CLick on the button below for a quick reference to common python programming structures.
Use the input() function to read text from the keyboard. When the Enter key is hit, all characters typed will be returned as a string. You will need to store them in a variable. If you are reading in numeric data you will need to convert it using float() or int().
Make sure to provide the user with a prompt before asking for data. You can either provide a prompt using a print() statement on the line above the input() function or passing a string as an argument to the input() function (as shown in the examples below).
Ex. Reading in a string:
name = input("Please enter your name: ")
You may want to prevent the user from putting incorrect input by automatically converting case for them. This example below ensures that even if the user types a 'q', it will be stored as a 'Q'.
choice = input("Please enter Q to quit").upper()
Ex. Reading in an integer:
age = int(input("Please enter your age: ")) #You must convert the string to an integer
Ex. Reading in a decimal number:
price = float(input("Please enter the price: ")) #You must convert the string to an float
See this link for a detailed explanation or search it on your own:
https://www.w3schools.com/python/python_conditions.asp
The condition of an if statement must be either a boolean statement, or something that the computer can evaluate to true or false. Only indented code will be treated as in the body of the if statement.
== equals (notice it is two equals signs)
!= does not equal
< , <= less than, less than or equal to
>, >= greater than, greater than or equal to
not : This will make a true be false and a false be true.
Example:
name = "Barney"
print(name == "barney") # Prints false because string comparison is case sensitive
print(not(name == "barney")) # Prints true
and : The entire boolean statement will be true only if BOTH conditions on either side of the and operator are true.
Example:
age = 19
name = "Gary"
print(name == "Gary" and age == 19) # Prints true
print(name == "Gary" and age < 19) # Prints false
or : The entire boolean statement will be true if AT LEAST ONE conditions on either side of the or operator is true.
age = 19
name = "Gary"
print(name == "Gary" or age == 19) # Prints true
print(name == "Gary" or age < 19) # Prints true
print(name == "gary" or age < 19) # Prints false
When comparing strings, use upper() or lower() to convert to a constant case to make comparison easier.
Example:
color = input("Please enter your favorite color: ").lower()
if (color == "blue"):
print("color is either Blue, blue, BLUE or any other permutation of case")
else:
print("name is not Steve")
For more details see:
https://www.w3schools.com/python/python_for_loops.asp
For loops always end BEFORE the end condition.
for i in range(10):
print(i, end = "") # Prints: 0 1 2 3 4 5 6 7 8 9
for i in range (1, 10):
print(i) # Prints: 1 2 3 4 5 6 7 8 9
for i in range(1, 10, 2):
print(i) # Prints: 1 3 5 7 9
Method 1 - By Index:
for i in range(len(names)):
print(names[i])
Method 2 - By Item:
for name in names:
print(name)
https://www.w3schools.com/python/python_conditions.asp
while (condition):
# Indented code will loop as long as condition is true.
# 'condition' can be a boolean value/variable or a boolean expression.
https://www.w3schools.com/python/python_lists.asp
names = []
names.append("Toopy")
names.append("Beanoo")
len(names)
names[0] # Access the first item in the list
names[0] = "Gary" # Changes the item at index 0 in the list
print(names[0]) # Prints the first item in the list
print(names[len(names) - 1] # Prints the last item in the list
names.pop(1) # Removes the item at index 1
names.remove("Gary") # Removes 'Gary' if it is in the list
Method 1 - By Index:
for i in range(len(names)):
print(names[i])
Method 2 - By Item:
for name in names:
print(name)
You cannot change an item in the list using this method, however, you can change its attributes if it is an object.