Python Cheat sheet
Useful tricks
# Terminate a Python script early.
quit()
# For 1 statement on multiple lines,
# use line continuation character (\).
# Good for blog post.
def __str__(self):
return "Name={}, Title={}, Hourly rate={}."\
.format( self.name, self.title, self.__hourly_rate )String
# Concatenation
s1 = 'Open'
s2 = 'Writings.net'
print( s1+s2 ) # Output: OpenWritings.net
# Object to string: Use str() function
import datetime
now_str = "Today is " + str(datetime.datetime.now())
print(now_str)
# Find and replace
string.replace(old_str, new_str, maxreplace) # maxreplace: Replace N occurrences matched.
# Replace using regular expression
import re
str="Example regex"
test = re.sub(r"[Ee]", "a", str) # axampla ragax
# Join: string.join(iterable); iterable = list, string & tuple
my_list = ['1', '3', '4', '5']
separator = ','
print( separator.join(my_list) ) # 1,3,4,5If statement
# Conditions
# Comparison operators
# == : Values are equal.
# != : Values are NOT equal.
# <> : Values are NOT equal.
# >= : Value is greater or equal.
# <= : Value is less or equal.
# is : Is the same object.
if True and b > a:
print("b is greater than a")
elif a == b and b is not None:
print("a and b are equal")
# Modulo
if i%2==0:
print('even')
else:
print('odd')List
my_list=[] # Empty list.
my_list=[1,2,3] # Create a list with some values.
print( len(my_list) ) # Size of my_list.
my_list[2] # Access the third element(Index starts at 0).
my_list[-1] # Get last element.
my_list.append('a') # Append a new value to my_list.
my_list.insert(0, 'first') # Insert 'first' at position 0.
del my_list[1] # Delete element at position 1.
my_list.remove('a') # Remove first element with value 'a'.
# Loop through a list.
for item in my_list:
print(item)
# Loop through a list using range.
for i in range(0, len(my_list)):
print(my_list[i])
# Loop through a list and at the same time, get the index too.
my_list = [1,3,5]
for (i, item) in enumerate(my_list):
print(i, item)
# Slicing
first_two = my_list[:2] # Get the first two items.
last_two = my_list[-2:] # Get the last two items.
portion_of_list= my_list[2:4] # Get items from position 2 to 4.
# For sorting, data type has to be the same. Can't mix int and string.
my_list=[1,2,3]
my_list.sort() # Sort list permanently in alphabetical order.
my_list.sort(reverse=True) # Sort list permanently in reverse alphabetical order.
my_list.reverse() # Reverse the order of the list. Loop
# Loop through a list & get index at the same time.
my_list = [1,3,5]
for (i, item) in enumerate(my_list):
print(i, item)Date & Time
import datetime
today = datetime.date.today()
print(today) # 2018-12-31
print("{}-{}-{}".format(today.year, today.month, today.day))
print(datetime.date(2011, 4, 13)) # 2011-04-13
print(datetime.date.fromtimestamp(1326244364)) # 2012-01-10
a_datetime = datetime.datetime(2011, 4, 13, 23, 33, 59)
print("{}-{}-{}".format(a_datetime.year, a_datetime.month, a_datetime.day))
print("{}:{}:{}".format(a_datetime.hour, a_datetime.minute, a_datetime.second))
print(a_datetime.timestamp())
# Convert date to string.
now = datetime.datetime.now()
print(now.strftime("%m/%d/%Y, %H:%M:%S")) # 04/04/2019, 12:45:08
# Convert string to date: string should match date representation.
# All directives(%): https://docs.python.org/3/library/datetime.html#strftime-and-strptime-behavior
a_date = datetime.datetime.strptime("21 June, 2018", "%d %B, %Y")
print(a_date) # 2018-06-21 00:00:00
a_date = datetime.datetime.strptime("12/11/2018 09:15:32", "%d/%m/%Y %H:%M:%S")
print(a_date) # 2018-11-12 09:15:32
# Add / Substract date
# timedelta(days=0, seconds=0, microseconds=0, milliseconds=0, minutes=0, hours=0, weeks=0)
today = datetime.datetime.now()
days_ago_delta = datetime.timedelta(days = 5)
days_ago_5 = today - days_ago_delta
print(days_ago_5)Function
def sum(a,b):
return (a, b, a+b)
print( sum(3,4) ) # Output: (3, 4, 7)Last updated
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