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157 lines
2.6 KiB
157 lines
2.6 KiB
# Python
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## Lesson Objectives
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1. Print a message
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1. Add a comment
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1. Create a variable and assign it a value
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1. Explain the different data types
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1. Perform calculations with variables
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1. Use string operations
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1. Create a list
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1. Access an element of a list
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1. Perform a set of commands depending on a situation
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1. Repeatedly perform a set of commands
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1. Get user input
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## Print a message
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You can print a message to the user
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```python
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print "hello!"
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```
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## Add a comment
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- Comments let you summarize what you're doing
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- They don't get executed
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```python
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# this will not be executed
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```
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## Create a variable and assign it a value
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```python
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a = "hello"
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print a ##print the value of the variable 'a'
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```
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## Explain the different data types
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There are lots of different types of data that you can use in python
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- String (text)
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- Integers (whole numbers)
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- Float (decimal numbers)
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- Booleans (True/False)
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You can convert one data type to another
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```python
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a = str(1) #a = "1"
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b = int("5") #b = 5
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c = float(4) #c = 4.0
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d = int(5.7) #d = 5
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```
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## Perform calculations with variables
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```python
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a = 1
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b = a + 1 #b = 2
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c = b * 3 #c = 6
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d = c - 1 #d = 5
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e = float(d) / 2 #e = 2.5
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f = d ** 2 #exponent: f = 25
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```
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## Use string operations
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```python
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a = "first string"
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b = "second string"
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c = a + " " + b
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```
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## Create a list
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You can create lists of things
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```python
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a = [1, 5, "some string", True, 5.6]
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```
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You can even have lists of lists
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```python
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a = [
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[1, 2, 3], #first row
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[4, 5, 6], #second row
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[7, 8, 9], #third row
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[10] #fourth row
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]
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```
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You can conceptualize a list of lists however you want
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**ACTIVITY: How would you change the previous example so that each inner list is a column?**
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## Access an element of a list
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Lists have elements stored at numerical indexes, starting at 0
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```python
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a = [1, 5, "some string", True, 5.6]
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print a[0] #1
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print a[1] #5
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print a[4] #5.6
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```
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## Perform a set of commands depending on a situation
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```python
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a = 22
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if a < 10:
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print "a is less than 10"
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elif a == 10:
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print "a is 10"
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else:
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print "a is greater than 10"
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```
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The conditions can be
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- < less than
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- > greater than
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- <= less than or equal to
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- >= greater than or equal to
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- == an exact match
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You can also compare strings:
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```python
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a = 'oh hai!'
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if a == 'oh hai!':
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print 'works'
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```
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## Repeatedly perform a set of commands
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```python
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a = 10
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while a < 20:
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print "the value of a is currently: " + str(a)
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a = a + 1
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```
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## Get user input
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You can get user input from the command like so:
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```python
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user_input = raw_input("Please enter something: ")
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print "you entered: " + user_input
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```
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