Python Cheat Sheet
Strings
Convert to list |
"this is a string".split() |
|
Repetition |
"string" x 3 |
|
Substring |
list[3:5] |
|
Formatting |
"""this is a %s text""" % ("nice") |
|
Reverse |
string[::-1] |
|
Every x'th char |
string[::x] |
|
Strip newline |
string.strip("\n") |
|
Raw strings |
r“hello world\n“ |
|
Convert anything into a string |
str(anything) |
|
Right-pad |
string.rjust(5) |
|
Left-pad |
string.ljust(5) |
|
Center string |
string.center(20) |
|
Length of a string |
len(string) |
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Go through the string char-by-char |
for char in string: |
|
Find a substring |
string.find(mystring, pattern, startpos, endpos) |
import string |
Zero-fill a number |
number.zfill(8) |
Lists
Create |
list = [] |
|
Destroy |
del list |
|
Fill |
list = [ "a", "b", "mpilgrim" ] |
|
Append element |
list.append(element) |
|
Remove element |
list.remove(element) |
by element |
|
del list[3] |
by position |
Remove slice |
del list[3:5] |
|
Append list |
list += [“a“, “b“] |
|
|
list = list1 + list2 |
|
|
list.extend(otherlist) |
|
Insert element |
list.insert(2, 'hello') |
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Iterate |
for element in list: |
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Check membership |
if element in list: |
|
|
if list.in("element") |
|
Get element |
list[5] |
|
Get slice |
list[3,4,7] |
|
|
list[3:7] |
|
Get/remove last element |
list.pop() |
|
Get/remove first element |
list.pop(0) |
|
Sort |
list.sort() |
|
|
list1 = list2.sorted() |
|
Reverse |
list.reverse() |
|
Repetition |
[1,2,3] * 2 => [1,2,3,1,2,3] |
|
Find element |
list.index("example") |
|
Number of occurences |
list.count('test') |
|
Join to string |
"".join(list) |
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Split to list list |
string.split(“;“) |
|
Create enumeration |
range(4) |
(gives [0,1,2,3]) |
|
range(1,9,3) |
(steps... gives [1, 4, 7]) |
List comprehension |
[element*2 for element in list] |
|
Apply function to members |
list = map(myfunc, [1, 24, 95]) |
|
|
list = map(myfunc, [1, 2, 3], [4, 5, 6]) |
(each list delivers one argument for the function) |
Return members for which a function gives true |
list = filter(myfunc, [1, 3, 4]) |
|
Reduce |
result = reduce(myfunc, [1, 2, 3] |
means: result = foobar(foobar(1, 2), 3) (use the results of the function as the argument of the next call of the function) |
Enumerate |
enumerate(['a','b','c']) |
gives: [[1,'a'], [2,'b'], [3,'c']] |
Take an element of each list |
for x, y in zip(list1, list2) |
|
Create a named enumeration |
(MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY) = range(7) |
Dictionaries
Create |
dict={} |
Fill |
dict = {"server":"mpilgrim", "database":"master"} |
Set element |
dict['a'] = 'b' |
Delete element |
del dict['a'] |
Clear |
dict.clear() |
Get keys |
dict.keys() |
Get values |
dict.values() |
Get key/value tuples |
dict.items() |
Check membership |
dict.has_key('key') |
Get member or zero |
dict.get( "key", 0 ) |
Iterate |
for key, value in dict.iteritems() |
Tuples
Create |
tuple = ("a", "b", "mpilgrim", "z", "example") |
Create with one value |
tuple = (3, ) |
Get element |
tuple[2] |
Get into variables |
x, y, z = tuple |
Misc
Swap values |
x,y = y,x |
Variables, References, Scopes
Create a reference |
a=[1,2,3] // b=a |
Copy a variable |
a=[1,2,3] // b=a[:] |
Famous quote of the python-list mailing list: You can tell everything is well in the world of dynamic languages when someone posts a question with nuclear flame war potential like "python vs. ruby" and after a while people go off singing hymns about the beauty of Scheme...
