- To determine how many items a tuple has, use the `len()`function:
```py
thistuple = ("apple", "banana", "cherry")
print(len(thistuple))
```
- To create a tuple with only one item, you have to add a comma after the item, otherwise Python will not recognize it as a tuple.
```py
thistuple = ("apple",)
print(type(thistuple))
#NOT a tuple
thistuple = ("apple")
print(type(thistuple))
```
- It is also possible to use the tuple() constructor to make a tuple.
```py
thistuple = tuple(("apple", "banana", "cherry")) # note the double round-brackets
print(thistuple)
```
### Set
- Set is a collection which is unordered and unindexed. No duplicate members.
- A set is a collection which is both unordered and unindexed.
```py
thisset = {"apple", "banana", "cherry"}
```
- Set items are unordered, unchangeable, and do not allow duplicate values.
- Unordered means that the items in a set do not have a defined order.
- Set items can appear in a different order every time you use them, and cannot be referred to by index or key.
- Sets are unchangeable, meaning that we cannot change the items after the set has been created.
- Duplicate values will be ignored.
- To determine how many items a set has, use the `len()` method.
```py
thisset = {"apple", "banana", "cherry"}
print(len(thisset))
```
- Set items can be of any data type:
```py
set1 = {"apple", "banana", "cherry"}
set2 = {1, 5, 7, 9, 3}
set3 = {True, False, False}
set4 = {"abc", 34, True, 40, "male"}
```
- It is also possible to use the `set()` constructor to make a set.
```py
thisset = set(("apple", "banana", "cherry")) # note the double round-brackets
```
### Dictionary
- Dictionary is a collection which is unordered and changeable. No duplicate members.
- Dictionaries are used to store data values in key:value pairs.
- Dictionaries are written with curly brackets, and have keys and values:
```py
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
```
- Dictionary items are presented in key:value pairs, and can be referred to by using the key name.
```py
thisdict = {
"brand": "Ford",
"model": "Mustang",
"year": 1964
}
print(thisdict["brand"])
```
- Dictionaries are changeable, meaning that we can change, add or remove items after the dictionary has been created.
- Dictionaries cannot have two items with the same key.
- Duplicate values will overwrite existing values.
- To determine how many items a dictionary has, use the `len()` function.
```py
print(len(thisdict))
```
- The values in dictionary items can be of any data type
```py
thisdict = {
"brand": "Ford",
"electric": False,
"year": 1964,
"colors": ["red", "white", "blue"]
}
```
### Conditional branching
```py
if condition:
pass
elif condition2:
pass
else:
pass
```
### Loops
Python has two primitive loop commands:
1. while loops
2. for loops
#### While loop
- With the `while` loop we can execute a set of statements as long as a condition is true.
- Example: Print i as long as i is less than 6
```py
i = 1
while i <6:
print(i)
i += 1
```
- The while loop requires relevant variables to be ready, in this example we need to define an indexing variable, i, which we set to 1.
- With the `break` statement we can stop the loop even if the while condition is true
- With the continue statement we can stop the current iteration, and continue with the next.
- With the else statement we can run a block of code once when the condition no longer is true.
#### For loop
- A for loop is used for iterating over a sequence (that is either a list, a tuple, a dictionary, a set, or a string).
- This is less like the for keyword in other programming languages, and works more like an iterator method as found in other object-orientated programming languages.
- With the for loop we can execute a set of statements, once for each item in a list, tuple, set etc.
```py
fruits = ["apple", "banana", "cherry"]
for x in fruits:
print(x)
```
- The for loop does not require an indexing variable to set beforehand.
- To loop through a set of code a specified number of times, we can use the range() function.
- The range() function returns a sequence of numbers, starting from 0 by default, and increments by 1 (by default), and ends at a specified number.
- The range() function defaults to increment the sequence by 1, however it is possible to specify the increment value by adding a third parameter: range(2, 30, 3).
- The else keyword in a for loop specifies a block of code to be executed when the loop is finished.
A nested loop is a loop inside a loop.
- The "inner loop" will be executed one time for each iteration of the "outer loop":
```py
adj = ["red", "big", "tasty"]
fruits = ["apple", "banana", "cherry"]
for x in adj:
for y in fruits:
print(x, y)
```
- for loops cannot be empty, but if you for some reason have a for loop with no content, put in the pass statement to avoid getting an error.
```py
for x in [0, 1, 2]:
pass
```
### Function definition
```py
def function_name():
return
```
### Function call
```py
function_name()
```
* We need not to specify the return type of the function.
