Python Cheat Sheet

list = []list[i:j]  # returns list subsetlist[-1]   # returns last elementlist[:-1]  # returns all but the last elementlist[i] = vallist[i:j] = otherlist  # replace ith to jth-1 elements with otherlistdel list[i:j]list.append(item)list.extend(another_list)list.insert(index, item)list.pop()        # returns and removes last element from the listlist.pop(i)       # returns and removes i-th element from the listlist.remove(i)    # removes the first item from the list whose value is ilist1 + list2     # combine two list    set(list)         # remove duplicate elements from a listlist.reverse()    # reverses the elements of the list in-placelist.count(item)sum(list)zip(list1, list2)  # returns list of tuples with n-th element of both list1 and list2list.sort()        # sorts in-place, returns Nonesorted(list)       # returns sorted copy of list",".join(list)     # returns a string with list elements seperated by comma

dict.keys()dict.values()"key" in dict    # let's say this returns False, then...dict["key"]      # ...this raises KeyErrordict.get("key")  # ...this returns Nonedict.setdefault("key", 1)

for item in ["a", "b", "c"]:for i in range(4):        # 0 to 3for i in range(4, 8):     # 4 to 7for i in range(1, 9, 2):  # 1, 3, 5, 7for key, val in dict.items():for index, item in enumerate(list):

str[0:4]len(str)string.replace("-", " ")",".join(list)"hi {0}".format('j')f"hi {name}" # same as "hi {}".format('name')str.find(",")str.index(",")   # same, but raises IndexErrorstr.count(",")str.split(",")str.lower()str.upper()str.title()str.lstrip()str.rstrip()str.strip()str.islower()/* escape characters */>>> 'doesn\'t'  # use \' to escape the single quote...    "doesn't">>> "doesn't"  # ...or use double quotes instead    "doesn't">>> '"Yes," they said.'    '"Yes," they said.'>>> "\"Yes,\" they said."    '"Yes," they said.'>>> '"Isn\'t," they said.'    '"Isn\'t," they said.'

int(str)float(str)str(int)str(float)'string'.encode()

[fn(i) for i in list]            # .mapmap(fn, list)                    # .map, returns iteratorfilter(fn, list)                 # .filter, returns iterator[fn(i) for i in list if i > 0]   # .filter.map

import rere.match(r'^[aeiou]', str)re.sub(r'^[aeiou]', '?', str)re.sub(r'(xyz)', r'\1', str)expr = re.compile(r'^...$')expr.match(...)expr.sub(...)

file = open("hello.txt", "r") # open in read mode 'r'file.close() 

print(file.read())  # read the entire file and set the cursor at the end of fileprint file.readline() # Reading one linefile.seek(0, 0) # place the cursor at the beggining of the file

file = open("hello.txt", "w") # open in write mode 'w'file.write("Hello World") text_lines = ["First line", "Second line", "Last line"] file.writelines(text_lines)file.close()

file = open("Hello.txt", "a") # open in append modefile.write("Hello World again")  file.close()

with open("welcome.txt", "r") as file:    # 'file' refers directly to "welcome.txt"   data = file.read()# It closes the file automatically at the end of scope, no need for `file.close()`.