Best Python Tips and Tricks

Question

1.Swap:
You can swap value of a and b in just one line using:
a,b=b,a
2.Reverse a string:
my_str="hello"
rvrse=my_str[::-1]
Output:"olleh"

3.Rotate list by n:
l[-n:]+l[:-n]
e.g l=[1,2,3,4,5]
a=l[-2:]+l[:-2]
Output: a=[4, 5, 1, 2, 3]
4.Del all elements of list:
lst = [1, 2, 3, 4, 5]
del lst[:]
Output: lst=[]
5.List comprehension:
vals = [expression for value in collection if condition]
even_squares = [x * x for x in range(10) if not x % 2]
even_squares>>>[0, 4, 16, 36, 64]

6.'==' vs 'is'
e.g
a = [1, 2, 3]
b = a
a == b>>>True
a is b>>>True
But ,
c = list(a)
a==c>>>True
a is c>>>False

7.sort() vs sorted:
sort() modifies the original list in place. The return value is None.
sorted() returns a new list.

8.collections.Counter lets you find the most commonelements in an iterable:
E.g;
import collections
c = collections.Counter('helloworld')

c>>>Counter({'l': 3, 'o': 2, 'e': 1, 'd': 1, 'h': 1, 'r': 1, 'w': 1})
c.most_common(3)>>>[('l', 3), ('o', 2), ('e', 1)]

9.Find permutation using itertools.
E.g;
import itertools
for p in itertools.permutations('ABCD'):
print(p)
Note:itertools.combinations can be used for finding combinations.

10.Importing everything from a module:
from <module_name> import *

11.Find factorial by:
import math
math.factorial(x)

P.S. During editing some points were deleted by accident.As I have no saved copy of this it will take some time to find them again.

Answer 1

[Cont.]
12.Boolean is treated as integer:
a=[5,4,8,7,1]
a[True]>>>4
a[False]>>>5

13.Conversion to binary and hexadecimal:
bin(a)>>>binary
hex(a)>>>hexadecimal

14.Calendar of any month:
import calendar
cal = calendar.month(2018,10)

15..Chaining of comparison operator.
n = 10
result = 1 < n < 20
print(result)>>>True

16.Use of ternary operators:
[on_true] if [expression] else [on_false]
x = 10 if (y == 9) else 20

17.Find the most frequent value in a list.
test = [1,2,3,4,2,2,3,1,4,4,4]
print(max(set(test), key=test.count))>>> 4

18.Create a dictionary from two releated sequences.
t1 = (1, 2, 3)
t2 = (10, 20, 30)
print(dict (zip(t1,t2)))>>>> {1: 10, 2: 20, 3: 30}

19.Transposing a Matrix
mat = [[1, 2, 3], [4, 5, 6]]
zip(*mat)>>>[(1, 4), (2, 5), (3, 6)]

20. A specialized tool often beats a general purpose tool
math.sqrt(x) is more accurate than x ** 0.5
math.log2(x) is more accurate than math.log(x, 2)
math.log1p(x) is more accurate than math.log(1+x)

21.If you are using python2 use:

from __future__ import print_function

It will stop you using print incorrectly in python3.

22.An if ... elif ... elif ... else sequence is a "substitute" for the switch or case statements
found in other languages.
Tip contributed by Eric Smith :Dictionaries can also be used as a substitute for switch case.

23. The lambda keyword in Python provides a shortcut for declaring small and
anonymous functions:
e.g
add = lambda x, y: x + y
add(5, 3)>>>8

24.Try running "import this" ;)

25.Find weekday of a certain date:
my_date=datetime.date(1996,7,19)

26.How to merge two dictionaries
in Python 3.5+
E.g

x = {'a': 1, 'b': 2}
y = {'b': 3, 'c': 4}
z = {**x, **y}
z>>>{'c': 4, 'a': 1, 'b': 3}

Answer 2

don't forget those:
a = (5, 6)
x, z = a
or
os.getattr('some attribute', name_of_object)
or
os.environ[]
or
print(some _color_encoding + r"")
or
string.strip() #especially in data output
or
os.fork()
os.execv
or
if not something
or
print("%s %r %i %b" % (string,string to repr(),integer,bytes object)
or
s = [{"hello" : "world"}]
print(s[0]["hello"])
or
str(subprocess.check_output(some shell,shell=True))
or
s = """\
some long
string
"""
I hope this helped :)

Answer 3

These are all on their separate own good subjects to start from when... making lessons here, if you know what mean 😏

Answer 4

@Mohammed Ateeb Ali Python Can Be Used In Web Development
Have You Ever Heard Of :
Flask
CherryPy
Django
CGI
Bs4 HTML parser
urllib which helps you to do more Interactive stuff with requests,files,downloads,etc
HTTP.server or HTTP.client
some supported html5 libs in pip

Answer 5

Cépagrave
Yeah But I Will Give Some Examples about Them :)

Answer 6

@mitali jadhavro
Here's Some Examples
Note: The Comment Was Very Long That It Tells Me No Connection
https://code.sololearn.com/cYmtzJc39BDu/?ref=app

Answer 7

Hi Mitali !
That's a great and very useful idea you got here !
Here is my suggestion : this thread is in Q&A and will become less visible after a while. And informations here will remain precious for pythonists though.
Conclusion :
You definitely should make a lesson of it in the lesson factory !
I understand you may feel it's not finished yet, but then it means you can make a multiple-chapters lesson !
I'll be the first happy to go there when I forgot this nice python trick which I know is existing but I don't remember exactly how it goes ...
Thanks for your sharing !

Answer 8

@mitali jadhavrao yes I just saw the post and saw some one or two line examples but I will give more examples 😊

Answer 9

Python Turtle and multi input codes are now available on Sololearn thanks to an awesome code by Burey!!!🐢
https://www.sololearn.com/post/30301/?ref=app

Answer 10

Amazing information!! 💚
and very helpful for SoloLearn challenges also 😂😂😂
thanks a lot for you help 💚💙

Answer 11

Cépagrave Hey thanks for the suggestion.I'll definately try to format it...make concepts even more clearer and submit this as a lesson.

Answer 12

[cont.]
27. How to sort a Python dict by value
E.g
xs = {'a': 4, 'b': 3, 'c': 2, 'd': 1}
sorted(xs.items(), key=lambda x: x[1])
>>> [('d', 1), ('c', 2), ('b', 3), ('a', 4)]

28.The "timeit" module lets you measure the execution time of small bits of Python code
E.g
import timeit
timeit.timeit('"-".join(str(n) for n in range(100))',number=10000)>>>0.3412662749997253

Answer 13

Here are some tips and tricks which I came across.
1). You can also print "Hello world!" By using import __hello__

2).You can Get factorial of any number just by typing
import math
math.factorial(num)

3). Use set to easily sort a given string in alphabetical order, and given number in the ascending order without repetition in both cases.
example =
input 1 = dcbadcba
‎output1 = abcd
‎input2 = 432123
‎output2 = 1234

4). use "try" and "except" statements in very small and simple programs to remove the unnecessary errors.
example =
import math
try:
print(math.factorial(int(input())))
except:
print("Invalid keyword")
it is very helpful if you are a beginner because it boosts confidence that you are tackling errors. And errors are very irritating at the beginning.

5). Use the time module to find out how much time it takes to give output of your code so that you can improve your program to take less time for the output.
example = This is the code for Fibonacci number
import time
def fibo(n):
old, new = 0, 1
if n == 0:
return 0
for i in range(n-1):
old, new = new, old + new
return new
n = int(input("FIBONACCI OF :"))
t1 = time.clock()
print("your fibonacci = {} ".format(fibo(n)))
t2 = time.clock()
print(t2-t1)

6). This is the most useful tip I can give
Use comments in codes which are complex to understand it clearly by yourself and it will also take less time to debug which will save your time.

7). Using The "exec" functions you can make 3 liner into one liner
Example=
a = 2
b = 2
print(a+b)

can be written as

print(exec("a = 2 \nb = 2\nprint(a+b)"))

8). Use "eval" function to solve integers which are in strings
Example =
print(eval("4**2"))

9).Bored.
Type "import this" to read very interesting tips for coding.

And finally the last tip
This will help you more than anything.
10). Practice! Practice! And Practice!

Thanks for reading!.

Answer 14

soon I will b studying python and the information here is really helpful. thanks for the effort

Answer 15

I have few key points...
Everyone knows about SET.

Let A={1,2,3}, B={2,3,4}

For Union,
A.union(B) or B.union(A) or A | B
Result = {1,2,3,4}

For Intersection,
A.intersection(B) or B.intersection(A) or A & B
Result = {2,3}

For Difference,
A.difference(B) or A-B
Result = {1}
B.difference(A) or B-A
Result = {4}

For symmetric difference,
A.symmetric_difference(B) or B.symmetric_difference(A) or A^B
Result = {1,4}

YOU CAN PLAY WITH MORE PROPERTIES OF SET THEORY... 😃

Answer 16

Eric Smith Excellent.👍
Use of dictionries was very thouthful.👍

Answer 17

Mitali Jadhavrao, Nice compilation. Thanks for sharing and appreciate your efforts on compiling, making example snippets, and posting it here, not like everyone subscribed to real Python or other sources anyways : )

(Edit)
also make best answer mark on [Continue] post so it appears on top, easier to read as continuous post.

Answer 18

Very useful information I got which I don't know! !! Thank you very much.

Answer 19

Perfect !
That will help many sololearners for sure !

Answer 20

thanks