Python Interviews: Difference between revisions
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= Modulus Operator =
* Check whether a number is divisible by another number using the modulus operator, %
n % k == 0
f = open('text.txt','r')
l = f.readlines()
f.close()
for i in l:
print(i.strip('\n'))
= Read Log File =
* Better way to open a file as it auto closed file, even on crash
<pre>
with open('/var/log/apache2/access.log','r') as file:
for line in file:
print(line.split()[3], line.split()[6], line.split()[8], line.split()[9])
try:
b = b +int(line.split()[9])
except:
pass
print(b)
</pre>
= List Comprehension =
[x**2 for x in range(1,11) if x % 2 == 1]
[x for x in range(1,11) if x % 2 == 0]
[start : stop : steps]
= Floor Division =
* Floor Division operator used for dividing two operands with the result as quotient showing only digits before the decimal point:
10//5 = 2
Line 23 ⟶ 43:
10.0//7 = 1.0
List is mutable while the Tuple is not.
A tuple is allowed to be hashed. E.g: using it as a key for dictionaries.
Line 30 ⟶ 50:
Tuple: b = (1,4,8)
Def can hold multiple expressions while lambda is a uni-expression function.
Def generates a function and designates a name to call it later. Lambda forms a function object and returns it.
Line 36 ⟶ 56:
Lambda supports to get used inside a list and dictionary.
= Optional statements in try-except block =
* Optional statements possible inside a try-except block:
“else” clause: It is useful if you want to run a piece of code when the try block doesn’t create an exception.
“finally” clause: It is useful when you want to execute some steps which run, irrespective of whether there occurs an exception or not.
Insert integer at position 5 at position 0:
Line 69 ⟶ 90:
print(max(b))
>>> a = [1,2,3,45,6,7]
>>> a
Line 79 ⟶ 100:
>>> hash(tuple(a))
1409902629973635913
= Eval Function =
You are given a polynomial of a single indeterminate (or variable), .
You are also given the values of and . Your task is to verify if .
Input:
1 4
x**3 + x**2 + x + 1
<pre>
a = (input()).split()
x = int(a[0])
k = int(a[1])
# Sol 1:
print (eval(input()) == k)
# Python 2:
print eval(raw_input()) == k
# Sol 2:
f = lambda x:eval(input())
print (f(x) == k)
</pre>
= Swap Case =
Python has built-in string validation methods for basic data. It can check if a string is composed of alphabetical characters, alphanumeric characters, digits, etc.
str.isalnum() checks if all the characters of a string are alphanumeric (a-z, A-Z and 0-9).
>>> print 'ab123'.isalnum()
True
str.isalpha() checks if all the characters of a string are alphabetical (a-z and A-Z).
>>> print 'abcD'.isalpha()
True
str.isdigit() checks if all the characters of a string are digits (0-9).
>>> print '1234'.isdigit()
True
str.islower() checks if all the characters of a string are lowercase characters (a-z).
>>> print 'abcd123#'.islower()
True
str.isupper() checks if all the characters of a string are uppercase characters (A-Z).
>>> print 'ABCD123#'.isupper()
True
<pre>
def swap_case(s):
a = ""
for i in s:
if i.isupper():
a += i.lower()
elif i.islower:
a += i.upper()
else:
a += i
return a
if __name__ == '__main__':
s = input()
result = swap_case(s)
print(result)
</pre>
<pre>
print ''.join([i.lower() if i.isupper() else i.upper() for i in raw_input()])
</pre>
<pre>
def swap_case(s):
a = ""
for let in s:
if let.isupper() == True:
a+=(let.lower())
else:
a+=(let.upper())
return a
print raw_input().swapcase()
print(input().swapcase())
</pre>
= Arrays & Reverse it =
<pre>
>>> input ="1 2 3 4 -8 -10"
>>> arr = input.split(' ')
>>> arr
['1', '2', '3', '4', '-8', '-10']
>>> arr[::-1]
['-10', '-8', '4', '3', '2', '1']
</pre>
= Regex =
Positive lookahead (?=REGEX_1)REGEX_2 (?=regex) t(?=s) matches the second t in streets.
Negative lookahead (?!REGEX_1)REGEX_2 (?!regex) t(?!s) matches the first t in streets.
Positive lookbehind (?<=regex) (?<=s)t matches the first t in streets.
Negative lookbehind (?<!regex) (?<!s)t matches the second t in streets.
= Sum Function =
lst = []
num = int(input('How many numbers: '))
for n in range(num):
numbers = int(input('Enter number '))
lst.append(numbers)
print("Sum of elements in given list is :", sum(lst))
= Convert Numeral System =
for i in range(0,10):
print(i, oct(i), hex(i), bin(i))
for i in range(0,10):
print(i, oct(i)[2:], hex(i)[2:].upper(), bin(i)[2:])
= Justify Text =
text.rjust(3,' ')
text.ljust(3,' ')
text.center(3,' ')
= Formatting =
[https://pyformat.info/ pyformat.info]
Old Method:
print('%s %s' % ('one','two'))
New Method:
print('{} {}'.format('one','two'))
Positional Index:
print('{1} {0}'.format(56,'ld'))
= Sorting =
listed ={}
plist = set(port_list)
listed.update({v:sorted(plist)})
for k,v in listed.items():
print("Tenant: ", k, "\nNo of Ports: ", len(v), '\n', [i for i in v if len(v) >0], '\n')
c = [1,5,2,3,9,6,2,0]
c.sort()
= Reverse a String =
'hello world'[::-1]
'dlrow olleh'
= Convert to Positive Number =
>>> a = -30
>>> abs(a)
30
* Interger can be positive or Negative:
>>> int(a)
-30
>>> -a
30
>>> c = 30.9
>>> int(c)
30
= "is" vs "==" =
a = [1,2,3]
b = a
c = [1,2,3]
print(a==c)
print(a is c)
Output:
True
False
= Dictionary =
a = {}
|
Latest revision as of 15:17, 1 May 2022
Modulus Operator
- Check whether a number is divisible by another number using the modulus operator, %
n % k == 0
Open a file
f = open('text.txt','r') l = f.readlines() f.close() for i in l: print(i.strip('\n'))
Read Log File
- Better way to open a file as it auto closed file, even on crash
with open('/var/log/apache2/access.log','r') as file: for line in file: print(line.split()[3], line.split()[6], line.split()[8], line.split()[9]) try: b = b +int(line.split()[9]) except: pass print(b)
List Comprehension
[x**2 for x in range(1,11) if x % 2 == 1] [x for x in range(1,11) if x % 2 == 0]
Slicing Operator
[start : stop : steps]
Floor Division
- Floor Division operator used for dividing two operands with the result as quotient showing only digits before the decimal point:
10//5 = 2 10.0//5.0 = 2.0 10.0//4 = 2.0 10.0//7 = 1.0
List vs. Tuple
List is mutable while the Tuple is not. A tuple is allowed to be hashed. E.g: using it as a key for dictionaries.
List: a = [1,3,6] Tuple: b = (1,4,8)
Lambda vs. def
Def can hold multiple expressions while lambda is a uni-expression function. Def generates a function and designates a name to call it later. Lambda forms a function object and returns it. Def can have a return statement. Lambda can’t have return statements. Lambda supports to get used inside a list and dictionary.
Optional statements in try-except block
- Optional statements possible inside a try-except block:
“else” clause: It is useful if you want to run a piece of code when the try block doesn’t create an exception. “finally” clause: It is useful when you want to execute some steps which run, irrespective of whether there occurs an exception or not.
List Operations
Insert integer at position 5 at position 0:
a.insert(0,5)
Delete the first occurrence of integer:
a.remove(6)
Insert integer at the end of the list:
a.append(9)
Sort the list:
a.sort()
Pop the last element from the list:
a.pop()
Pop 3rd element:
list1.pop(2)
Reverse the list:
a.reverse()
Max of List(print runner-ups score):
arr = [1,4,2,6,7,6] mx = max(arr) b = [j for j in arr if j != mx] print(max(b))
List to Tuple Conv & Hashing
>>> a = [1,2,3,45,6,7] >>> a [1, 2, 3, 45, 6, 7]
>>> tuple(a) (1, 2, 3, 45, 6, 7)
>>> hash(tuple(a)) 1409902629973635913
Eval Function
You are given a polynomial of a single indeterminate (or variable), . You are also given the values of and . Your task is to verify if .
Input:
1 4 x**3 + x**2 + x + 1
a = (input()).split() x = int(a[0]) k = int(a[1]) # Sol 1: print (eval(input()) == k) # Python 2: print eval(raw_input()) == k # Sol 2: f = lambda x:eval(input()) print (f(x) == k)
Swap Case
Python has built-in string validation methods for basic data. It can check if a string is composed of alphabetical characters, alphanumeric characters, digits, etc.
str.isalnum() checks if all the characters of a string are alphanumeric (a-z, A-Z and 0-9).
>>> print 'ab123'.isalnum() True
str.isalpha() checks if all the characters of a string are alphabetical (a-z and A-Z).
>>> print 'abcD'.isalpha() True
str.isdigit() checks if all the characters of a string are digits (0-9).
>>> print '1234'.isdigit() True
str.islower() checks if all the characters of a string are lowercase characters (a-z).
>>> print 'abcd123#'.islower() True
str.isupper() checks if all the characters of a string are uppercase characters (A-Z).
>>> print 'ABCD123#'.isupper() True
def swap_case(s): a = "" for i in s: if i.isupper(): a += i.lower() elif i.islower: a += i.upper() else: a += i return a if __name__ == '__main__': s = input() result = swap_case(s) print(result)
print ''.join([i.lower() if i.isupper() else i.upper() for i in raw_input()])
def swap_case(s): a = "" for let in s: if let.isupper() == True: a+=(let.lower()) else: a+=(let.upper()) return a print raw_input().swapcase() print(input().swapcase())
Arrays & Reverse it
>>> input ="1 2 3 4 -8 -10" >>> arr = input.split(' ') >>> arr ['1', '2', '3', '4', '-8', '-10'] >>> arr[::-1] ['-10', '-8', '4', '3', '2', '1']
Regex
Positive lookahead (?=REGEX_1)REGEX_2 (?=regex) t(?=s) matches the second t in streets. Negative lookahead (?!REGEX_1)REGEX_2 (?!regex) t(?!s) matches the first t in streets. Positive lookbehind (?<=regex) (?<=s)t matches the first t in streets. Negative lookbehind (?<!regex) (?<!s)t matches the second t in streets.
Sum Function
lst = [] num = int(input('How many numbers: ')) for n in range(num): numbers = int(input('Enter number ')) lst.append(numbers) print("Sum of elements in given list is :", sum(lst))
Convert Numeral System
for i in range(0,10): print(i, oct(i), hex(i), bin(i))
for i in range(0,10): print(i, oct(i)[2:], hex(i)[2:].upper(), bin(i)[2:])
Justify Text
text.rjust(3,' ') text.ljust(3,' ') text.center(3,' ')
Formatting
pyformat.info
Old Method:
print('%s %s' % ('one','two'))
New Method:
print('{} {}'.format('one','two'))
Positional Index:
print('{1} {0}'.format(56,'ld'))
Sorting
listed ={}
plist = set(port_list) listed.update({v:sorted(plist)})
for k,v in listed.items(): print("Tenant: ", k, "\nNo of Ports: ", len(v), '\n', [i for i in v if len(v) >0], '\n')
c = [1,5,2,3,9,6,2,0] c.sort()
Reverse a String
'hello world'[::-1] 'dlrow olleh'
Convert to Positive Number
>>> a = -30 >>> abs(a) 30
- Interger can be positive or Negative:
>>> int(a) -30 >>> -a 30
>>> c = 30.9 >>> int(c) 30
"is" vs "=="
a = [1,2,3] b = a
c = [1,2,3]
print(a==c) print(a is c)
Output: True False
Dictionary
a = {}