python.md

Python cheatsheet

• List is a collection which is ordered and changeable. - Allows duplicate members.
• Tuple is a collection which is ordered and unchangeable. Allows duplicate members.
• Set is a collection which is unordered and unindexed. No duplicate members.
• Dictionary is a collection which is unordered, changeable and indexed. No duplicate members.

Arrays (lists)

x = len(cars)

• append to array cars.append("Honda")
• add to position cars.insert()
• remove item cars.pop(1)
• get item thislist[1]
• get last item thislist[-1]
• range of indexes thislist[2:5]

The search will start at index 2 (included) and end at index 5 (not included).

thislist[2:]

From 2 ot end

• range of negative indexes thislist[-4:-1]

from index -4 (included) to index -1 (excluded)

• check if item exists if "apple" in thislist:
• join two lists list3 = list1 + list2
• remove last item list.pop()

For loops

colors = ["red", "green", "blue", "purple"]
for i in range(len(colors)):
    print(colors[i])

for color in colors:
    print(color)

presidents = ["Washington", "Adams", "Jefferson", "Madison", "Monroe", "Adams", "Jackson"]
for num, name in enumerate(presidents, start=1):
    print("President {}: {}".format(num, name))

Sets

## or
thisSet = set()
for x in thisset:
  print(x)

• add to set thisset.add("orange")
• add multiple items thisset.update(["orange", "mango", "grapes"])
• length len(thisset)
• remove thisset.remove("banana")
• check if in set print("banana" in thisset)
• remove last item thisset.pop()
• set from array s = set(lst)

Dictionary

  "brand": "Ford",
  "model": "Mustang",
  "year": 1964
}

• access items x = thisdict["model"] or x = thisdict.get("model")
• change val thisdict["year"] = 2018
• loop Print all key names

  print(x)

• print all values

  print(thisdict[x])

• return the values

  print(x)

• Loop through both keys and values

  print(x, y)

• check if key exists

  print("Yes, 'model' is one of the keys in the thisdict dictionary")

• adding items thisdict["color"] = "red"
• remove item thisdict.pop("model")
• remove last inserted item thisdict.popitem()
• empty dict thisdict.clear()
• copy a dict mydict = thisdict.copy()