Basic syntax
Basic syntax
Indentations
Indentation or TAB, 2/4 spaces - whitespaces used to delimit program blocks - instead of punctuation or keywords, it uses indentation to indicate the run of a block.
for i in [1, 2, 3]:
if i == 3:
print("Number 3 found!")
else:
print("Number:", i)
In C we need to use brackets({
and }
) to delimit blocks of code:
void foo(int x)
{
if (x == 0) {
bar();
baz();
} else {
qux(x);
foo(x - 1);
}
}
In Python the same role goes to indentations which make code much easier to read:
def foo(x):
if x == 0:
bar()
baz()
else:
qux(x)
foo(x - 1)
Easter egg describing the "love to braces"
from __future__ import braces
SyntaxError: not a chance
Indentation must maintain the constant level for same level of nesting.
This is correct:
if condition:
do_something1()
do_something2()
This is incorrect:
πͺ Code:
if condition:
do_something1()
do_something2()
π Output:
If code block is not big it is allowed to use inline form:
if condition: do_something1()
else: do_something2()
for x in range(10): print(x)
And it is possible to specify few statements on the same line using ;
:
a = [x for x in range(10) if x % 2]; f = open("tmp.txt", "w"); f.write(a); f.close()
These two examples are not readable so used very rarely.
Identificators and reserved words
Naming rules:
can have only alphabetical characters, numbers and
_
can't start with number
case sensitive
can't be one of reserved keywords
Reserved words (which can't be used as variable names):
and del from not while
as elif global or with
assert else if pass yield
break except import print True
class exec in raise False
continue finally is return
def for lambda try
Comments and documentation strings
#
- starting with this symbol everything till the end of line is ignored
a = 12345 # This is comment
# This is comment too
# Continuing our comments
Doc string - first string of module, function or class. These string are used by IDEs, help auto-generating scripts etc. It is possible to specify multiline string by using starting and ending with triple quotes("""
or '''
).
πͺ Code:
def f():
'''
Some nice function (the best in the world)
:no params:
:return: None
'''
help(f)
π Output:
Help on function f in module __main__:
f()
Some nice function (the best in the world)
:no params:
:return: None
Or:
πͺ Code:
f.__doc__
π Output:
'\n Some nice function (the best in the world)\n \n :no params:\n :return: None\n '
### Naming rules
Variables can only contain letters, numbers, and underscores. Variable names can start with a letter or an underscore, but can not start with a number.
Spaces are not allowed in variable names, so we use underscores instead of spaces. For example, use student_name instead of "student name".
You cannot use Python keywords as variable names.
Be careful about using the lowercase letter l and the uppercase letter O in places where they could be confused with the numbers 1 and 0.
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