#set document(title: "10.4 Conditionals and looping in dictionaries", author: "OpenStax / XYZ Homework")
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== 10.4#h(0.6em)Conditionals and looping in dictionaries


  
    
=== Learning objectives


    By the end of this section you should be able to


    - Write a conditional statement to check for a key/value.
- Write a for loop to iterate over elements of a dictionary.


  
  
    
=== Conditionals for dictionary


    Conditional statements can be used with dictionaries to check if certain keys, values, or dictionary items exist in the dictionary or if a value satisfies a particular condition.


    #examplebox("Example 1")[Templates and examples of a conditional statement on a dictionary][
#figure(table(
  columns: 1, align: left, inset: 6pt,
  [dict.items()],
  [\# (key, value) in dictionary.items()

movies = {"The godfather": 1974, "Interstellar": 2014}

print(("Interstellar", 2014) in movies.items())],
  [True],
))


      #figure(table(
  columns: 1, align: left, inset: 6pt,
  [Conditionals on values or keys],
  [\# dictionary\[key\] operand test\_value

movies = {"The godfather": 1974, "Interstellar": 2014}

print(movies\["The godfather"\] \< 2000)],
  [True],
))


      #figure(table(
  columns: 1, align: left, inset: 6pt,
  [dict.keys()],
  [\# key in dictionary.keys()

movies = {"The godfather": 1974, "Interstellar": 2014}

print("Interstellar" in movies.keys())],
  [True],
))


      #figure(table(
  columns: 1, align: left, inset: 6pt,
  [dict.values()],
  [\# value in dictionary.values()

movies = {"The godfather": 1974, "Interstellar": 2014}

print(2014 in movies.values())],
  [True],
))
]


    #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[
#emph[Conditionals on dictionaries]


      Given the dictionary fruit\_count = {"apple": 2, "orange": 5, "pomegranate": 1}, answer the following questions.
]


  
  
    
=== Looping on a dictionary


    Looping over a Python dictionary is a way to iterate through key-value pairs in the dictionary. Looping in a dictionary can be done by iterating over keys or items. When looping using keys, keys are obtained using the keys() function and are passed to the loop variable one at a time. When looping over items using the items() function, both the key and value for each item are passed to the loop variable.


    #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[
#emph[A for loop over a dictionary retrieves each key in the dictionary]


      
    for key in dictionary: \# Loop expression
      \# Statements to execute in the loop

    \# Statements to execute after the loop
]


    #examplebox("Example 2")[Iterating over a dictionary][
#figure(table(
  columns: 1, align: left, inset: 6pt,
  [dict.items()],
  [zip\_codes = {"Berkeley": 94709, "Santa Cruz": 95064, "Mountain View": 94030}

for key, value in zip\_codes.items():
  print(key, value)],
  [Berkeley 94709
Santa Cruz 95064
Mountain View 94030],
))


      #figure(table(
  columns: 1, align: left, inset: 6pt,
  [dict.keys()],
  [zip\_codes = {"Berkeley": 94709, "Santa Cruz": 95064, "Mountain View": 94030}

for key in zip\_codes.keys():
  print(key)],
  [Berkeley
Santa Cruz
Mountain View],
))


      #figure(table(
  columns: 1, align: left, inset: 6pt,
  [dict.values()],
  [zip\_codes = {"Berkeley": 94709, "Santa Cruz": 95064, "Mountain View": 94030}

for value in zip\_codes.values():
  print(value)],
  [94709
95064
94030],
))
]


    #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[
#emph[Loops on dictionaries]
]


  
  #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[
#emph[Character count in a string]


    Given a string value, calculate and print the number of occurrences of all characters using a dictionary.


    
    Input:
    string\_value = "This is a string"
    
    Prints {"T": 1, "h": 1, "i": 3, "s": 3, " ": 3, "a": 1, "t": 1, "r": 1, "n": 1, 
    "g": 1}
    string\_value = "This is a string"

\# Create a dictionary and count the number of occurrences of characters
]


  #notebox("Note", rgb("#8a94a6"), rgb("#556666"), rgb("#f7f8fa"))[
#emph[Calculate the total number of fruits]


    Given a fruit\_count dictionary that contains information about fruits and the count of each fruit, calculate the total number of fruits across all fruit types.


    
    Input:
    fruit\_count = {"banana": 2, "orange": 5, "peach": 5}
    
    Prints 12
    fruit\_count = {"banana": 2, "orange": 5, "peach": 5}

\# Calculate and print the total number of fruits
]